I don’t know anything about wheelchairs, but there’s a similar very high-margin market for eyeglasses. Freakonomics did a podcast about it:

https://freakonomics.com/podcast/why-do-your-eyeglasses-cost...

Frames have crazy 100x markups and the market is dominated by a small number of companies. They interviewed people from Warby Parker (a newer, more inexpensive brand) and even they said they had to raise prices so they didn’t seem like knock-offs.