I Tracked Every "On Offer" Purchase for Six Weeks — Most of Them Cost Me Money

Log kept 16 March to 26 April 2026 · Published: 28 October 2026 · Last updated: 28 October 2026 · Reading time: ~8 minutes · The log, the receipts and the photographs in this post are my own.

I have a habit I did not think of as a habit. When something is on offer and I am standing in front of it, I buy it. Not always, but often enough that when I started writing it down, I found twenty-three instances in six weeks.

The yellow sticker, the "was £4 now £2.50" card, the two-for-one on the end of the aisle. Every one of them framed as a saving, and every one of them felt like one in the moment. So for six weeks I wrote down every discounted thing I bought, and next to it, before I picked it up, one question: would I buy this at full price?

The answer, twenty-three times over, split into three groups. And when I added them up, the offers had cost me money. Not saved me less than I thought. Cost me money, outright, by about £10 across six weeks.

How I tracked it

I did not do this from receipts afterwards. Receipts tell you what you paid. They do not tell you whether you wanted the thing, and that is the entire question. So the log was written in the shop, on my phone, before the item went in the basket.

For each discounted purchase I recorded four things: what it was, what I paid, what it would have cost at full price, and my answer to the question. That last one is the only one that required any honesty, and writing it before picking the item up was the only way to get an honest answer. If I had done it at home afterwards, I would have justified every purchase. I know that because I tried it in week one and caught myself doing it.

The log, week three. Two prices and a yes or no. The no column is the one that turned out to matter.

The three groups

Twenty-three purchases, £87 paid, £123 at full price. On the face of it, a saving of £36.

Group	Items	Paid	Full price	What it actually was
Already on my list	8	£34	£47	Things I had written down before I left the flat. A real saving, £13.
Would buy eventually	6	£22	£30	Pantry staples and things I use weekly. I would have bought them within a month. A real saving, £8, just earlier than planned.
Would never have bought	9	£31	£46	Not a saving of any kind. £31 spent on things I did not want, at a discount I invented by pretending I wanted them.
Total	23	£87	£123	Headline saving £36. Real position: £10 worse off.

The £36 on the bottom row is what the supermarket would like me to think I saved, and what I would have told you I saved if you had asked me on any of those six Saturdays. The real position is £13 plus £8 minus £31, which is minus £10.

The gap between those two numbers is £46, and £46 is exactly what the nine unwanted things would have cost at full price. That is the whole trick. A discount on something you were never going to buy is not a discount. It is a price, and you paid it.

What the nine were

I want to be specific, because the list is more embarrassing than the total.

Three were reduced bakery items: a pack of rolls, a cake, a loaf. All bought late in the day at half price, all eaten within about a day, none of them on any list. Two were a "two for £5" deal on a snack I do not normally buy, which is exactly why there were two of them. Two were end-of-aisle items with a "was" price on the card: a jar of something, which I used without ever registering it, and a bag of something, which never got opened at all. One was a seasonal thing that was 70% off, which I bought in March and threw away in April. And one was a large bag of coffee, because it was on offer and I drink coffee, except I had a full bag at home and I knew it.

A reduced section just like this one, week four. The three bakery items came from a shelf like this.

None of those nine were disasters. That is the point. Each one was £2, £3, £4. There was no single moment where I could have pointed at a mistake. There were nine small moments where I did not ask a question, and the total was £31.

And the coffee is the one that annoys me, because I did ask the question. I stood there with the bag and thought "would I buy this at full price?" and the answer was yes, obviously, I drink coffee. But the question is not "would I buy this thing at some point in my life." It is "would I buy this today, if it were full price, given what I already have at home." I had a full bag at home. The honest answer was no, and I gave myself a dishonest one because the offer made the dishonest answer feel reasonable.

The six that were fine

The six in the middle group are the interesting ones, because they are a real saving and they still taught me something.

These were pantry things: tinned tomatoes, pasta, oil, a bag of rice. Things I buy every few weeks. When they are on offer I buy two instead of one, and I will use them. The saving is genuine — £8 across six weeks — and there is nothing wrong with it.

But I noticed something about how I feel in those moments, which is that it feels like the same feeling as the nine. The end-of-aisle "was £4 now £2.50" produces exactly the same small hit of cleverness as the tinned tomatoes at 60p off. The body cannot tell the difference between a real saving and an invented one, and that is why the invented ones work.

The only difference is whether you were going to buy the thing anyway, and that is not a feeling. It is a fact about your list, and you either have one or you don't.

The thing I got wrong

I assumed an offer was a discount on a decision. It is not. It is a decision that has been made for you, by the shop, at a moment when you are least able to make one.

That framing took six weeks to arrive at, and it came from noticing that the nine unwanted purchases were not stupid. Each one was a thing a reasonable person might buy. What made them wrong was not the item, it was the moment: I was standing in front of a yellow sticker with a trolley and no list, and the offer had already done the deciding before I arrived.

This is the third time a money experiment has landed on the same underlying thing, which is the difference between a decision and something that merely looks like one. The subscription audit found that annual renewals were payments I had never decided about. The no-spend month found that the want list worked because it turned an impulse into a written decision. This one found that an offer is the opposite: a written decision, in the shop's handwriting, that I mistake for my own.

The rule I came out with is not "don't buy offers." It is this. An offer is only a saving if the item was on your list before you saw the sticker. If it wasn't, the offer has not saved you anything. It has cost you the full reduced price of something you did not want.

What I would do differently

I would have started the log with a list. Not because a list would have stopped the nine, but because it would have made the question answerable in the shop. "Would I buy this at full price?" is hard to answer honestly when the item is in your hand and the sticker is yellow. "Is this on the list?" is easy, and it is not a feeling.

And I would have counted the nine separately from the start, rather than discovering them in week six. For the first three weeks I was logging the two prices and the yes/no, and I was treating every purchase as one category. It was only when I sorted them into three groups that the number appeared, and by then I had already spent most of the £31.

The receipts for the six weeks. The highlighted lines are the twenty-three, and the total paid for them is £87.

Should you do this?

The log, no. Six weeks of writing in your phone before every purchase is more effort than the £10 is worth, and I would not do it again.

The question, yes, and it costs a second. Next time you are standing in front of something with a sticker on it, ask one thing: was this on my list before I saw it? If yes, buy it, and take the saving, because it is real. If no, you are not saving anything. You are about to pay the full price of something you were not going to buy.

That is the whole finding. Twenty-three offers, £36 of savings, and a real position of £10 worse off, because nine times I did not ask a question I could have asked in one second.

Frequently asked questions

Would you have bought the nine anyway, later?

Two of them, maybe. The rolls and the loaf, because I buy bread every week and the timing worked out. The other seven, no. The cake, the two snack packs, the jar, the bag of something, the seasonal thing and the second bag of coffee would all have been £0 if I had walked past the sticker, and I know that because I have walked past that shelf a thousand times and bought nothing.

Isn't buying reduced food good, because it stops it being wasted?

That is the argument I would have made for years, and I still think it is partly true. But it is not my job to rescue a supermarket's overstock, and it only holds if I eat the thing. Of the nine, seven got eaten and two got thrown away (the seasonal thing and the unopened bag), so the food-waste benefit was not the point either. If you want to reduce food waste, the experiment on that is here, and it is about buying less, not buying discounted.

Did the offers change what you ate that week?

Yes, and I had not expected that to matter. The reduced bakery items became breakfast for three days in week four, which meant I ate less of what I actually wanted. That is a small cost and it is not in the £31. I have not put a number on it, and I am mentioning it because the arithmetic in this post is only the money.

What about loyalty cards and member prices?

I did not track those and I am not going to guess. My suspicion is that member-only prices behave more like the middle group than the last group, because you tend to buy the same things every week and the discount lands on a regular purchase. But that is a suspicion, not a result.

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About this post

Written by Maha Alkumaish. I write about the routines and systems that survive a real working week, tested on myself before they get written about. The log and the receipts behind this post are my own.

All photographs in this post are my own. I was not paid or sponsored by any brand mentioned, and there are no affiliate links in this post. More about me and how these experiments are run.

Related reading on this blog:

• I audited every subscription I pay for, where the payments I never saw were decisions I had never made
• I did a no-spend month with three exceptions, where writing the wants down turned an impulse into a decision I could look at
• I ate only from my freezer for a week, where 36 of 47 items had no meal attached, which is what a freezer full of offer purchases looks like two years later
• More Money & Simplicity posts