Lowest prices I've seen for those trapped on Z390/Z370 motherboards who want an upgrade to fast i9s (much cheaper than deranged eBay seller prices). Otherwise go AMD Ryzen 3000 series or 10th Gen Intel if building new. KF model in main link is overclockable but has iGPU disabled. All of these i9s have 8 Cores and 16 Threads
Make sure your Z390/Z370 is not a piece of junk VRM-wise if you want to overclock these i9s. Reference table of all Z390 motherboards provided below (aim for white zone motherboard or above for decent ability to OC i9-9900K/KF CPUs):
https://www.overclock.net/forum/attachment.php?attachmentid=…
Delivery appears reasonable (under $11 for me in NSW).
i9-9900K (overclockable and iGPU enabled)
i9-9900 (locked CPU and iGPU enabled)
my maximus 10 hero isnt listed but should be ok for 9900 after a bios update