The formula

Cost per use = (price + running costs − resale value) ÷ number of uses

Most people run only the first term and stop. The other two frequently reverse the answer.

The example that reframes expensive purchases

A 200 winter coat against a 60 one:

The expensive coat is cheaper per wear, and it is also cheaper in absolute terms over five winters — 200 against 300 for five replacements. This is the entire case for buying durable goods once, and the arithmetic supports it whenever the durability difference is genuine.

The example that goes the other way

The metric is not a licence to buy expensive things. It is savage on anything that goes unused:

The gym rows are the same product at a sixfold difference in real price, determined entirely by behaviour. The bread maker is the archetype: a reasonable price and a catastrophic cost per use, because the estimate of future enthusiasm was wrong.

The two terms people forget

Running costs. A printer at 80 that consumes 60 of ink a year costs 320 over four years, not 80. Cheap hardware subsidised by expensive consumables is a deliberate business model, and cost per use only exposes it if you include the consumables.

Resale value. This is the term that most often rescues an expensive purchase. A 900 phone sold after three years for 300 has a net cost of 600. A 400 phone worth 40 after three years costs 360 net. The gap narrows from 500 to 240, and if the expensive one lasts a year longer the comparison inverts. Durable brands with strong second-hand markets — tools, cameras, some furniture and clothing — carry a hidden discount that the sticker price hides completely.

Where the metric misleads

• You will overestimate future uses. This is the dominant error, and it is systematic rather than random. Everyone buying skis intends to ski more than they do. Estimate from your last twelve months of actual behaviour, not your intentions.
• It ignores capital constraints. The 200 coat is only the better buy if you have 200. Advising someone with 60 that they should spend 200 is not financial insight; borrowing at 24% to buy the durable option usually destroys the saving.
• It ignores value per use. A mattress used 2,900 times over eight years and a pillow used the same number of times have similar cost-per-use profiles and very different consequences. The metric treats all uses as equal, and they are not.
• It feeds sunk-cost thinking. Once bought, the price is gone. Using something you dislike to improve its cost per use is a fallacy — the correct move for a bad purchase is to sell it or give it away and stop paying storage in attention.
• It cannot price enjoyment. A book read once at 15 per use is not a bad purchase. Some things are consumed, not amortised.

Questions people actually ask

What is a good cost per use?

There is no universal threshold — it is only meaningful comparing alternatives for the same job. Comparing a coat to a kettle tells you nothing.

How do I use it before buying rather than after?

Set a use threshold in advance and be pessimistic. Decide that the item must reach a target cost per use, work backwards to the required number of uses, then ask honestly whether you have done that thing that often in the past year.

Does it apply to subscriptions?

Very well, and this is where it finds the most money. Divide the annual cost by actual sessions used. Streaming and software subscriptions you touch twice a month often have an absurd cost per use, and they renew silently.

Is my purchase data stored?

No. Prices and use counts stay in your browser and nothing is transmitted or saved.