In fact, AMD is launching a Ryzen Threadripper 2920X with 12 cores and 24 threads for USD 649 (https://www.anandtech.com/show/13443/amd-announces-availability-of-12-and-24core-threadripper-2-cpus-coming-late-october ).
This may be a contender to the i9-9900K. And, at this price point, it may mean that AMD is expecting the i9-9900K to cost in the USD 550-600 range.
You have to pay 300-400 USD just for the motherboard, there is a reason why Threadripper doesn't matter really. Threadripper is no contender for Intels or AMDs mainstream.