Intel's new generation wasn't supposed to launch until early 2018 and suffers from very limited availability. A consumer reached out to Newegg to discover what's going on and heard that the e-tailer is still waiting on new supply.
The Core i5 8600K currently has estimated shipping dates of "15 to 20 days", while the Core i7 8700K isn't expected to be in stock until "3 to 5 "weeks" from now:
Newegg has apparently ordered over 3000 units of the Core i7 8700K CPU alone, in order to keep pace with demand (these have been well-received chips as you can see on TPU's own reviews). Newegg expects these to come in at around a "3 to 5 weeks" time-frame. What separates this particular availability problem from being simply an issue of overly high demand is that Intel's Coffee Lake processors were already expected to be limited in availability even before they were launched.So there you have it. Coffee Lake-S was a very limited volume launch and new supply isn't coming anytime soon.