Cost per use is the number that decides whether something was expensive

Two purchases, the same money, different outcomes

Price is a single number attached to a moment. It is also the only number most people have when they decide, which is why it does so much work it is not equipped for. What a purchase actually costs is the price divided by the number of times the thing gets used, and that second number is invisible at the till.

An illustration. A coat costing 300 that gets worn four hundred times over six winters has cost 0.75 per wearing. A coat costing 80 that is worn a dozen times before it stops looking right has cost close to 6.70 each time. The cheaper coat was more than eight times as expensive by the only measure that describes what happened.

This is not an argument that expensive things are secretly cheap. It is an argument that price alone cannot tell you which of two options was the better use of money, because it contains no information at all about the denominator.

The denominator is the part you are guessing

Cost per use is arithmetic, but only one of its two inputs is known. The price is on the label. The number of uses is a forecast made by someone who currently wants the item, which is close to the least reliable moment to be forecasting anything about it.

The reliable failure is an optimistic denominator. Equipment for an activity not yet taken up, clothing for a life not currently being led, a machine for a routine that has not existed for years — each is priced against a use count that exists mostly in intention. The honest question is not how often you could use it, but how often you used the last comparable thing you bought.

Past behaviour is the best available evidence here and it is free. If a similar purchase two years ago has been used nine times, nine is a far better estimate than the hundred you can picture. That correction alone changes more purchasing decisions than any budgeting method.

Durability shows up in the denominator, not the price

Better construction rarely makes something perform noticeably better on the first day. What it usually does is raise the number of uses before the thing fails, which means it acts on the bottom of the fraction rather than the top. That is why the value of durability is invisible at the moment of purchase and obvious three years later.

Repairability works the same way and is easy to overlook. An item that can be resoled, restrung, rewired or fitted with a new battery has a denominator that can be extended for a fraction of the replacement price. One sealed against repair has a hard ceiling on its use count no matter how well it was made.

Both of these are probabilistic rather than guaranteed. A well-made thing can still be lost, outgrown or ruined, and paying more buys a better expected lifespan, not a promised one. That distinction matters when the price gap is large.

Where the arithmetic stops being useful

Cost per use handles repeat-use goods and handles almost nothing else. Something bought for one occasion has a denominator of one by design, and dividing by it tells you nothing you did not already know. The right comparison there is against hiring, borrowing or doing without, not against a longer-lived alternative.

It also ignores resale. An item that retains value can be sold, so its true cost is the price minus what comes back, divided by the uses in between. And it ignores the cost of holding things: storage, maintenance, insurance where relevant, and the low but real chance that something bought for the long term is superseded before the long term arrives.

There is one more limit worth naming. Cost per use says nothing about whether you could afford the price in the first place. A purchase with excellent long-run arithmetic that has to be borrowed for at a high rate can easily be the worse decision, and that comparison depends on circumstances the arithmetic does not see.

What the number is genuinely good for

Its best use is comparing options inside a single category, where the alternatives are interchangeable and the only real question is how long each will last. It is also the clearest way to think about upgrading something that still works, because it forces you to price the remaining life you would be throwing away.

It is useful in the opposite direction too. Run the sum on something you already own and use constantly and the result is often startlingly low, which is a reasonable defence against replacing a perfectly good item because a newer one exists.

Treat it as one input rather than a rule. Money decisions of any size involve affordability, timing, what else the money was for and how much uncertainty a household can carry, and none of that fits into a fraction. Where the sums are significant, a regulated adviser is the right place to take the whole picture.