Just play cabin feaver on extreme with as little amount of guys as possible.
This is all I do and before i knew it I became BOSS!! we beat it with 3 guys on extreme and my only hack is a no-recoil hack, and my clan mate used a few respawns but he didn't use them till round 17!!
when u have a full room (8 guys) you dont get as many kills (LESS GP), and that causes guys to run outside and ks which causes the zombies to rush in causing EPIC FAIL!
(btw, my buddy has elite so we kicked our forth guy at the beginning of round 1 lol)
You will still get just about this much even if you only make it to round 10, but ONLY USE 3-4 PLAYERS!!