If you want to save money... make sure not to add a hotswappable control panels..
or you find yourself searching ebay for tons of old crap...
but it depends on how nice you want... and what you already have.
I'll assuming you start with a kit. You will save about 100 bucks if you build it yourself... but I can't do work that nice. Its a good deal as long as shipping isn't outrageous.
You COULD use an existing monitor... but I think they look like crap compared to a true arcade monitor.... assuming you have an extra monitor that upgrade will cost you $200 for a 19" monitor + 80 for the arcadeVGA + $15 I think for a vidamplifier.
Or you could go SVid TV. This will cost the amount of the monitor and probably a 30-40 ati video card (make sure its "built by ATI" not "powered by ATI").
Next... your controls
1)
www.therealbobroberts.com will save some over happs... you can figure this cost out
2) you might consider getting a tstick ultra (8/4 way swappable from top panel). This is a really good thing... but costs an extra 15 or so per joystick.
Controller?
1) cheapest... hack some usb gamepads... lots of extra work... cabling much uglier... about 12bucks
2) Get an IPac or Keywiz. 30-40 base... goes up if you want 4 player cabinet capible.
Then you have..
actlabs gun? (40) are you going to hack it in a real arcade gun case (20 ebay)
trackball?
2 1/4" ($26 + 10 (mounting kit) + $10 hacked mouse)
3" (60ish + mounting + hacked)
Speakers?
use pc speakers - 15ish
hack to real arcade speakers - add another 20
What am I missing here?
time?