Which US law requires RID to be built into drones flown in the US?
Sure, some people might use a hack like that to fly illegally, but there's nothing inherently illegal about it in general.
It's the "Trust" part of the Trust Test that is the failure point. Look at the "range test" videos that idiots used to post about how far they were able to cover with their drone. Most of those idiots knew the difference between VLOS and BLVOS...
Most of the listings have language like that in the eBay listing that OP had shared:
It's one hundred percent on the buyer to pay any tariff charges. The chances of recovery of any duties from the seller would be nil.
All of the Mavic Pro models weigh more than 250g. If this is first gen Mavic Pro, then it's a moot point because it didn't have the hardware to support RID without an external module.
It was less of thinking and more of a "hold my beer" process.
A lot of people who do this are less informed about what could happen. If you are a member of this site or anything like it, you are more informed than the guy who bought a drone on...