Intel Core i9-7980XE Skylake X 18-Core 2.6 GHz $1971.88 current price.
AMD Ryzen Threadripper 16 core was up there too but has dropped under $1000 I think.
You won't find those current CPUs in thrift store boxes. (and when you do 8 years from now, they will be worth maybe $50-150)
I recall Intel bleeding edge CPUs were $1000 and up 20 years ago also. They dropped in price very quickly, but out the gate, the top end stuff has always been $1000-$2000
Late last year I upgraded my 10 year old quadcore processor ($266 back then but an incredible bang for the cheap buck at the time) with a faster drop in replacement that I picked up for $28 on eBay and got about a 20% CPU performance boost. That processor was $530 when I bought mine for $266.
For about double ($60) I could have gone one more step up to the top of that CPU family tree and gotten another 5% relative performance boost and more heat (that processor came out 6 months later, was also $530, and pretty much just factory overclocked version of the replacement I bought.)
The extreme versions that came out at the same time were $1000-$1500, and are under $50 on eBay (not sure why - they are significantly faster but also 50% more wattage/heat).
High end CPUs start out very high, tail off quickly, and lose a lot of relative value with time. But it is possible to find $25 to $100 (current eBay value) or so CPUs in the thrifts - just may be a bit unlikely as those types are typically not in mainstream machines. The enthusiasts likely just keep them, sell them on eBay, gift them, and what you will find are the junk CPUs they upgraded from.
