How this is calculated
cost per use = price ÷ (uses per month × 12 × lifespan in years)
Cost per use divides the price by every time the thing actually serves you: price ÷ (uses per month × months of lifespan). It's the metric that vindicates the expensive daily and convicts the cheap occasional — $200 boots worn 20 times a month for three years cost 28 cents a wear, while a $40 kitchen gadget used twice costs $20 a use.
The honest input is the middle one. We buy for the person we plan to be (daily gym! weekly baking!) and use as the person we are. Estimating uses from last month's actual behavior, not next month's intentions, is the entire skill of this calculation — and the reason the fanciest exercise equipment has the worst cost per use in most homes.
The metric also rehabilitates quality: if the well-made version lasts three times longer, it can cost twice as much and still win per use. That's the 'buy it for life' argument in arithmetic form — durability is a discount, spread over years.
Frequently asked questions
What's a 'good' cost per use?
There's no universal bar — a $3-per-use rain jacket that keeps you dry beats a $0.10-per-use trinket you don't care about. The number's job is comparison: between candidates, or between the purchase and renting/borrowing instead.
How does this apply to subscriptions?
Directly: monthly fee ÷ monthly uses. A $60 gym membership at 12 visits is $5 a visit — compare that to drop-in prices and the answer writes itself in either direction.
What about resale value?
Subtract expected resale from the price before dividing — it's a rebate on durability. Quality items with strong resale markets (tools, cameras, some furniture) get dramatically cheaper per use this way.