Depends where you're looking. There's a few potential causes.
1. Sellers are out of their mind, asking ridiculous prices
2. Buyers are actually buying at that price, and sellers are simply pricing accordingly.
3. Collector value (not likely, but a possibility).
Where are you looking specifically? Sites like Amazon or eBay (third party sellers) list things for crazy prices. I'm not sure why, but surely nobody is buying at those prices.
Regardless of the asking price, a chip like a 4790K sells frequently for around $200.
https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=i7-4790k&LH_Complete=1&LH_Sold=1&rt=nc&_trksid=p2045573.m1684
A pretty fair price, consider it's performance is still really good for the money. A nice...