UPDATE: Regular box 10700K now cheaper at Amazon AU ($334.34) https://www.amazon.com.au/Intel-i7-10700K-3-80GHz-LGA1200-Cl...
These eBay options may still be better for some if paying with gift cards and/or you want the free games.
Plenty of Ryzen deals here lately but these are good alternatives on the Intel side, more cores and cheaper than both 5600X (for the i7) and 5800X (for the i9). I'd assume cheapest ever for these.
The regular box 10700K is also available from Computer Alliance here for $356.15 plus you may be able to claim a couple of free games (Chivalry 2 and Hitman 3).
Note that the 10700K (Avengers Edition) linked to in this deal says "Last one" available but they seem to keep restocking (they likely have many more, but doing this as a tactic to get people to panic buy). It's "In Stock" on their website.