I didn’t know it had a name but marginal utility sounds like the concept behind the early form of eBay, before it became a corporation. You can still find people giving stuff away on there but that sort of exchange has now moved to places like Freegle, Freecycle and Facebook Marketplace, to a lesser extent. What people value has always been a mystery to me, I would be horrible in business. Most of my decisions are pretty much utilitarian, aside from food and drugs. I am happy in a junk yard, salvaging materials and components, that stuff feels under utilised and valuable to me.