It’s expensive for sure, but that’s mostly because powered chairs are made by medical companies and in comparatively low numbers.
A mobility scooter has almost all components a powered chair has, and these can be had for as little as €1000.
The technology behind a powered chair isn’t hard.
And even if we use the high price of a power scooter: How much does it cost to make a paraplegic person walk?
That does make sense. But still, making a powered chair is not at all technologically difficult. You need the chair, two motors and an input system that works for the user.
Sure, if there’s a lot of bespoke parts and manual labour, coupled with basically no economy of scale, it’s going to be expensive. But it’s not difficult.