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.