My vehicle has just a simple chassis made of angle iron plus pieces of 2x4 plus plywood. But it's been re-designed several times. Granted I could look at it a different way, and say I built 3 different vehicles, each for substantially less than $1,000:
Prototype 1: $273 (abandoned before I spent a lot)
Prototype 2: $490 (completed through some field tests, which showed poor performance)
Final version: $384
The problem is versions 1 and 2 didn't work, but I had to spend the money to find that out.