Quoted from BrewinBombers:Here's an option that might be easy: that budget would get you ~ 9 NIB Stern Pro. Buy 8 NIB Stern from a Distributor - and your new best friend - and find 2 more budget friendly DMD games.
Aerosmith
Spiderman VE
GOT
GB
TWD
MET
KISS
and if they have backstock you might be able to get a deal on WWE and Avengers.
People will rip my suggestion for having some games in here that they don't love, but if you're flexible on the titles like you say, I have a feeling a distributor might be able to make something work for you with the same ease - or more - as someone with a collection.
With a $50k budget, I would not waste your time with a bunch of stern machines. Take your time and get the games you want. Get some popular collectible ones (FH, TAF, MM, TZ, TS, etc....). Mix in a stern new game as well or a JJP.
Just my opinion...