The formula, honestly
Divide the total cost of owning a thing by the number of times it serves you. Done properly, the numerator is price grown at your market return over its life, plus upkeep as it's paid, minus honest resale — because money resting in a coat also missed the market. The denominator is realistic uses: what the thing actually did, not what the purchase speech promised.
The lie
The boutique version divides an optimistic price by an aspirational number of wears and calls the result thrift: "$2,800, but you'll wear it 200 times a year for a decade — pennies!" Wardrobe research and every honest closet audit agree that most garments deliver a small fraction of planned wears; a fifth is a fair prior. At a fifth, the pennies become tens of dollars, and the "investment piece" reveals itself as consumption with a mission statement. The lie is never in the division — it is always in the denominator.
Where the logic genuinely holds
Things used often, long, and roughly as planned: the everyday bag, the boots that see four winters, the mattress, the office chair, the espresso machine that retires a daily café habit. For these, paying up for durability is arithmetic, not aesthetics — doubling the price while tripling the honest life is a strict win, and the formula proves it. It also produces the one comparison that settles rent-versus-buy for occasionwear: a per-wear figure against the rental price is a fair fight.
What it cannot price
Joy. The dress worn twice, to two weddings that mattered, may be the best money on the page — but it is a pleasure purchase, and it should be bought as one, from the budget where pleasures live, without borrowing thrift's vocabulary. The formula's job is to stop that borrowing, not to forbid the purchase.
The house position
The Cost Per Use instrument runs the honest version — capital cost in, upkeep compounded, resale off, and a scenario row for "a fifth of planned use", which is the row to read first. For objects that are really positions wearing a hobby's clothes, the Collectible as a Position instrument is the adult version of the same question.