well then we just don't see eye to eye. Clearly - to me - the x299 is a better option now than any motherboard option previously available to consumers. 4 core to 18 core options on one series (at a time when generation CPU changes have yielded less than 10% IPC for the last 6 years - nearly down to 2-3% in the last generation --- meaning we've hit a bit of ceiling on clock speed and IPC improvements until some major overhaul -- so now failing Mhz improvements and IPC improvements we must go wide and 18 cores is very very wide.
so yeah --- looking back through history --- in previous generations you could consider an upgrade from a 4 core to a six core on the same board. (MANY were limited to ONLY 4 core variants) So yeah --- this x299 has future legs!
You've got lots of flexibility with PCI-E lanes when they are needed, you've got the newest tech currently available with no outstandingly obvious bottlenecks for the future (m2 2280 PCI-E variants like the 960 EVO are both stupid fast and stupid cheap (IE $160 for an OS drive that reads at 3,200 MB/s -- that won't seem slow for a LONG time to come) -- you've got USB 3.1 and even when new tech comes out you've got the bandwidth via both CPU cores and PCI-E LANs to handle new tech upgrades into the forseeable future. You've got plenty of memory bandwidth with four channel memory support. It's a very versatile time to upgrade or buy new!
BTW -- While I don't have a problem with a used CPU from the likes of ebay -- I do have a greater fear of a used motherboard from the likes of ebay. Too many things can go wrong or become intermittent problems with a motherboard that you don't know how it was handled or why they are truly selling the part.
So yeah --- I just straight up disagree with you. I'd gladly speed $150-$200 extra on the x299 motherboard and CPU over an older --- (currently) similar performing part. --- in simple anticipation of all these things we've discussed. Personally I would probably buy the 6 core at $389, with the plan to upgrade to a 10+ core when/if the need arises. Put a filter search on ebay and BIN when the opportunity arises.
I think I can agree to disagree, we are talking opinions after all (even though I'm right and you're clearly wrong )