Why are there no quadruped 'wheelchairs'?

So the problem is more powering for time in use more than anything else? Interesting. Shouldn’t there be at least some wired prototypes then?

The only one I clicked on was $12k new, which is in fact cheaper than a new car.

I suspect that some of the used chairs will also be cheaper than some used cars, but probably not all used chairs cheaper than all used cars given that one can acquire a used car for <$1k and I'd wager that most used chairs would be higher than that.

All that said, simple economics likely explains the discrepency. The market for cars is far greater than the market for chairs, the new inventory is higher, and the used inventory is higher as well. There are dozens of car manufacturers competing for the demand incentivizing price competition where as there are relatively fewer chair manufacturers competing for less demand leading to less incentive to compete on price. The smaller demand will also account for smaller R&D budgets, fewer and lower quality engineers, etc. Not to besmirch those doing hard work, but the chair manufacturers likely cannot support the level of salary that car manufacturers can to attract top quality engineers.

There could also be regulatory and insurance issues with insurers refusing to buy top quality chairs when the ones that don't climb will cover a majority of use cases. The policies will also likely gaurantee "a chair" rather than "whatever chair you want".

And, of course, it was only quite recently that robots that could climb were invented, and the ones that do so did not originally do so with very high centers of mass, so it will have been more recently still that someone figured that out. And, of course, it's still more complicated than that given that if your dystopian dog bot falls over it's likely undamaged whereas the chair tipping would likely result in a cracked skull meaning that you'd have to design a system that is quite a bit more robust and also likely combine that with liability waivers.

Just reasoning from principles that it is a difficult problem to solve for a relatively smaller addressable market size reveals that there's really no wonder that there are only a few companies and that it will have been a recent development.

It's not as if we have a preponderance of engineers who are eager to accept lower salaries than they are capable of earning. I'm sure there are a few, but it cannot be a vast sum.