Oh this is an awesome comment. I love talking about this part of UBI
I studied Economics in school and dived deep into UBI. Some interesting facts/research for you:
(Fun fact) The US already has UBI, just a super watered down version. It's called EITC (Earned Income Tax Credit). It's a Nixon brainchild and was thought they could use UBI to reduce the inefficiencies of such a big government. I.e. get one nice UBI check that covers healthcare, retirement, insurance, education, food, housing, etc. blah blah blah, and you can shut down a bunch of federal government agencies that are pretty inefficient.
The car dealership thing happened because of a variable that we often discount: information (or knowledge). The car dealership knew exactly how much money was coming out and who got it (mostly), and they knew it was a one-off not an ongoing thing. A lot of UBI macro research guesses that we'd see some small inflationary pressure at the beginning when it's new, but then return to normal as it becomes part of every day life. And even if it does, the benefits strongly outweigh the benefits and the Fed has other tools to reign in inflation to balance the affect out.
Caveat, this knowledge is 20+ years old. I may be way off base.