The grandparent comment is not claiming that $2k is under $800, but instead that Intel would be able to charge a higher price for the i9 if the TR was not on the market.
I got my 1950x for $699 a few months ago. Its been $699 for a while at Microcenter.
The "price-competitive" i9-7900x is 10-cores for $799, and seems to be the best price-competitive comparison. Better single-thread, better at AVX512 tasks, but weaker in general purpose multithreading due to having fewer cores.