I was on a budget when I built my old X79 and skimped on the CPU, choosing a 3820. Just as I was about to purchase a 3930k a good friend who's always on a tight budget had a failure so I sold him what I had on the cheap. I just recently upgraded my GPUs and am going to hand my old 980s down to him but I thought while I'm at it I'd explore the option of upgrading the 3820 especially since I rolled a critical miss on the silicon lottery and it's never overclocked very well.
I know someone with a few 3930ks and depending on his mood I can probably snag one for ~125. However I'd be happy to entertain other options around the ~$150 price range.
MAIN RIG:
Maximus X | i7-8700k | 32GB Corsair Vengeance | 2x EVGA 1080ti FTW3 | EVGA Supernova G3 1000 |