Funny you mention that, because that’s yet another case where it’s expensive to be poor. If you’re living paycheck to paycheck, barely making ends meet, you likely don’t have the cash flow to stock up on a sale. So rather than buying 18 months worth of TP when there’s a sale + coupon on the 64 pack, you are buying the 4 pack at regular price that costs twice as much per unit.
Take boots, for example. He earned thirty-eight dollars a month plus allowances. A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of OK for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars. Those were the kind of boots Vimes always bought, and wore until the soles were so thin that he could tell where he was in Ankh-Morpork on a foggy night by the feel of the cobbles.
But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that'd still be keeping his feet dry in ten years' time, while the poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet.
This was the Captain Samuel Vimes 'Boots' theory of socioeconomic unfairness.”
And for the kinds of goods I buy, in most cases it doesn't hold up. Cheap shoes might be only 25% of the price of good shoes, but in my experience last 50% as long, costing less overall. Compound that with other chances of loss (getting dusty in the back of a cupboard and eventually being thrown out in a declutter), and cheap works out far cheaper
And the point Samuel Vimes is making goes far beyond a simple "If you buy cheap, you buy twice." It extends that basic knowledge by realizing that some people have no other option than to buy cheap, forcing them to spend resources over and over and over again and still get a worse result in the end, and how this is a fundamental and systemic social unfairness.