Continue your patience, you will be rewarded. Those prices will come down very soon on ebay. I suspect x299 cpus values will be say 50% of its amd ryzen 3000 equivalent. Could find even better deal locally.
This is my own thought on pricing using my 7920x as sample. Note my own evaluation is lower though than most people though. My target sale price is looking like 500usd x 30% return =150usd. Hence, why i rather help out friends of mine get an well deserved upgrade than try to sell it.