All the games you priced, MvC, SFA and SFA2 are all CPS2 systems, pretty much stuff that could still pull in a buck on route, making it worth that much more..
Look for an old Street Fighter 2 (not Super Street Fighter 2 - thats CPS2), or even a Street Fighter 1 cabinet and buy a new board for it. Also keep an eye out for "Fighters History", the clone Data East made which got them sued by Capcom (Capcom lost) - those go cheap. Also keep an eye out for a mid to late 90s cabinet that'd be easy to convert, (Data East or Konami cabs make good candidates) or a dynamo or other generic cabinet designed for conversions.
25" monitors always jack up the price. Good luck at the auction. Show up early, pick a few that you like, and pick a maximum price to pay - don't be like me and get all competitive. I'm not allowed at auctions anymore. If you can throw your voice, try throwing out "I hear that ones cursed!" or "I hear it's full of dead kittens", etc.
Don't make the newbie mistake of being so eager to buy something you wind up with a piece of crap - check for water damage and other signs that it'll take an assload of work to rejuvinate it, and dont be afraid to walk away. Your 100 dollar cabinet could easily wind up costing more than that 600 dollar main event if you nickel and dime yourself rebuilding it (80 in controls here, 50 bucks for wires there, etc). There's plenty of cabinets out there, dirt cheap - free sometimes.. You just have to be patient, you'll find them when you aren't looking.
I visited a warehouse a few moths ago, I wasn't looking to buy a cabinet (wanted to scavenge the junk pile for a coin door and some other parts), but ended up walking out with a 25" data east cab for 100 bucks and a really georgeous time pilots cocktail for 65, both in great condition and working (well easy fixes).. Dude was in the frame of mind of 'the more of these other people move out means the less I have to'.