How do you know they are good? Did you use one for an extended period of time?

A set of wheels and a cushion do not make a good wheelchair, if you want to live an active life. Please see https://news.ycombinator.com/item?id=41721976

I am from Europe and chairs are a bit less expensive here, but an "active" wheelchair is usually more than 2k$ anyway, often closer to 3k$. And some are much more than that (for instance if you want a soldered chassis)