Intel's Core i9-9900K and Core i7-9700K processors are at record lows right now. With the price cuts, the introduction of Comet Lake-S and the consistent pressure from AMD's Zen 2 chips, Intel's Coffee Lake chips have been just going downhill.
In August, Intel had issued price reductions up to 25% on some of its most popular 9th Generation models. For this occasion, however, it might just be retailers trying to rid themselves of the remaining Coffee Lake processors. As per CamelCamelCamel's data, the Core i9-9900K and Core i7-9700K have dropped to $359.99 and $289.99, respectively.
Even at $359.99, the Core i9-9900K isn't that great of a bargain. The Core i7-10700K is faster than the Core i9-9900K in both general and gaming performance and only costs $20 more. The Core i9-9900K, on the other hand, is on the dying LGA1151 platform. The only reason that we can see for someone to pick up a Core i9-9900K is if the person already owns a LGA1151 motherboard and wants to upgrade from a slower processor, say like a Core i3. If you're starting from scratch, it's just a better decision to roll with the Core i7-10700K and LGA1200 platform, which is ready for PCIe 4.0 when Rocket Lake drops.
The Core i5-10600K is on par with the Core i7-9700K when it comes to gaming performance, However, the Core i7-9700K is still a bit ahead of the Core i5-10600K for single-and multi-thread workloads.
A few months ago when the Core i7-9700K costed $339.99 and the Core i5-10600K went for $262, the latter would have been the easy pick. However, the Core i7-9700K now sells for $289.99, and the Core i5-10600K retails for around $280 when there's no promotion.
Once again, the Core i7-9700K should be a good option for existing LGA1151 owners that want a decent processor without having to shell out money for another motherboard. If you're putting together a system for the first time, you'd be better served with Comet Lake or AMD's Zen 2 offerings. However, if time isn't of the essence, it's even better to wait for Zen 3, which AMD will announce on October 8.