Not a wheelchair (thanks Steve!)

only 4 to 5 thousand dollars apiece. That's as much as a used car. Hell, even a couple used cars.

 But, they have one thing right, that's the design, and anyone with a welder can probably make one just from watching this video, for a couple hundred dollars.

 I'd say the first accessory to add to these rigs, is a portable solar charging panel system, so when it's not on the move, a fast couple lever movements would expand a folding solar panel system, maybe even mounted as a roof https://justacarguy.blogspot.com/2017/11/one-of-coolest-things-i-found-at-sema-7.html

The second improvement would be quick change wheels, and the other set of wheels would be extemely focused on better traction, like, knobby motorcycle tires, sand paddle tires... or even, caterpillar tracks. Doesn't need to move a tank, just some small simple, little cat tracks that would work much better in the woods, sand, snow, mud.