Yeezys aren't exactly cheap when they're brand new, but they accumulate value rapidly after they're released because they're all limited-edition runs. Kanye West knew exactly what he was doing when he released his special sneakers; make the runs short so there's high demand, and therefore build a collector's market for them later. We bet he has hundreds of them kept back so he can sell them for their peak price in a few years' time.
The specific Yeezy which has seen the most significant rise in value is 2012's Air Yeezy 2 Red Octobers, which sold for $245 when they first hit the shelves. If you still have a pair in their box somewhere, you can expect to receive more than seven thousand dollars if you decide to sell them. Given the pace of escalation, it might be best advised to hang on to them for another five years and see if the price goes even higher!