I don't get the stock market analogy nor associated display of price volatility, but the ability to find quality, unused athletic shoes that are "off market" but still desirable, is near-wonderful! Paying a higher premium - much higher in some cases - isn't fun, & that's where patience comes in, because for instance, some of the items come from outside of the USA.
Maybe I just didn't do something correctly, but the inability to send an item as a gift - for reasons of security & of the stock market model maybe - wasn't enjoyable.