I just paid for one for my son and it was $672.

At those prices, he damn well better be autistic. You don't want to pay $672 just to find out he's weird.

I talked to my wife about getting evaluated myself, but apparently that's too much money to just confirm what everyone already knows.

I mean it depends on what kinda test it was. This $30 was probably just some app, judging by the transaction description. A test by a professional is still like 500€+ here in Germany (at least the few I found when looking for a diagnosis), since it's usually not covered by insurance