eBay has the Intel Core I7-7700K 4.2GHz Quad-Core Kaby Lake CPU (BX80677I77700K) for $310 - $15 off with coupon CSAVE15OFFMARCH (Ends 3/20 at 8PM PT; requires Paypal) = $295 with free shipping. List price: $350. Features socket LGA 1151, intel 200/1001 series chipset compatibility, intel HD graphics 630, intel turbo boost 2.0 technology.
Walmart has the AMD RYZEN 7 1700X 8-Core Desktop CPU (YD170XBCAEWOF) for $355 - $59 off with in-store pickup discount = $296. List price: $400. Features AMD SenseMI Technology, frequency: 3.4 GHz(Max:3.8 GHz), 16MB L3 Cache, 4MB L2 Cache, DDR4 Support.