alt Hacker NewsIt's a relatively small market so the up front capital and ongoing labor costs are probably pretty restrictive. Those parts are more expensive than you realize though with the wheels being the most expensive part if I had to wager, they're critical, specialized, and need to stand up to a lot of abuse.
I toured the Trek factory when they still made them in the US. They'd already drunk from the font of Goldratt wrt to Just in Time, but they would set up each day pretty much to make one model of bicycle for the whole day. Parts, tooling, paint booth, everything. The only thing that changed was sizes, and a model of bike tends to have the same geometries across all sizes. 78º angle here, 99º angle there. That may not be optimal for the rider but it's how you keep prices down and keep product lines from getting confusing.
If that's true of wheelchairs, you can get some economies of scale even if sizes vary. If it's not, then maybe that's one of the things we should tackle.