That is more than what my 3 cheapest Mame cabs cost combined. Maybe even more than I spent on all four of them. 
The one I've just started building is probably gonna cost around $30(and I'm actually building it too

, all that money is for the cost of wood, paint and plexiglass!). It's gonna be a bartop, so it needs less materials. I'm hacking an old keyboard I already had, using a 14" monitor I already had, using a pentium 100mhz I already had, using buttons I already have, and using some joysticks that I got 4 for $20(those microleaf joysticks). What makes it even cheaper is, I'm getting the wood, paint, and plexiglass as part of my Christmas presents. So this thing is gonna cost me nothing to make.