the permit itself is valid for either 1 or 3 years... But its only valid in Thailand for 90 days after every entry. You can leave and come back and reset these 90 days, but after 90 days in country you need a Thai license to legally drive.
If you know otherwise, I would like to see official Thai information about that change.
"No clue where you heard 80k usd a year needed that's definitely not the case"
You are right it is not the case, but you were then told where it IS a case, to clear up the confusion for yourself and others who might wonder where this assumption originated.
It's not that hard to see why this was relevant here.
Tourist visas and visa exemptions does not allow you to work in Thailand, not even remotely.
DTV allows you to work remotely, as long as your customers/clients are not Thai.
People are being questioned more when they bounce around a lot on regular tourist visas and visa exemptions, and a lot are being denied entry because Immigration thinks they are trying to stay long term on them.