Those prices are pretty decent, unless they are located in SWVA, in which case you should be shocked to see such high prices, and send me the contact info, so I can school this guy on realistic prices ;-) Just kidding.. Pick them up, thats as cheap as I ever see decent working cocktails. Keep in mind galaga will need new control panels to support a multi board.
Per 60-n-1s, my feeling is that its a good thing as long as you can preseve the original. Buy new control panels/joysticks (you need the sticks, and overlays anyway), and a jamma harness, and wire it into the existing power supply. Leave the existing wiring alone and the boards in place. You'll have to add a couple of wires for the lights if you want them. This way, you keep the value of the game when you convert it back.