It's certainly the case that anyone who needs an item but doesn't have cash on hand for it is going to pay more (by borrowing and paying interest), which isn't

It's certainly the case that anyone who needs an item but doesn't have cash on hand for it is going to pay more (by borrowing and paying interest), which isn't quite the same phenomenon but boils down to the same conclusion: in many cases, it costs more to be poor. However I will agree there are likely more cases where buying the cheaper product is the most economical option even in the long run - obviously true for perishable items, but e.g. when deciding to buy 2nd hand vs new, and yes, even for things like clothes, there are clearly examples of items whose price bears little relation to their likely longevity. Though I would suggest in general that a $100 pair of shoes is likely to last more than 4 times longer than a $25 pair.