To sneakerheads, fashion and aesthestics value far more than function and performance. Sneakerheads being a [large] subset of the current streetwear trend, exclusivity is another major factor for inflated prices in streetwear and sneakers.
Timed and location specific drops of exclusive, limited edition, special colorway variants of shoes, clothes and all other types of popular gear raises value. As mentioned, StockX majorly drives the market, and the exclusivity leads the savvy (or obsessed) consumer to seek advantages over others: bots, bulk buying, captcha solving, DDoSing, proxies, and the usual exploits are employed. The prices and value may be ridiculous but obviously, it's worth it to someone and there's lots of money to be made.