[Chuck Moreland]

I have a set of longacre scales. They are not cheap, but Souk is right.

Although you could fab something up for a material cost of significantly less than $1k, you will burn a lot of hours making setup anywhere near as functional as the longacres.

The pads that the tires rest on are very sturdy (and need to be). This alone is a challenging design and fabrication task. Then you have the electronics.

Like so many DIY projects, do it for fun / challenge / enjoyment. But the hours that will go into it would make it impractical...unless you place no value on your time.