If you are dead set on making cabs, the only way you're going to make any money is if you repro pac, ms pac, or galaga cabs and sell them to someone refurbing an original. Even then I don't think your going to be making any money , relative to the time invested.
Building a complete functioning cab is probably the only solvent method, but you will find out that not many people are too keen on making money off of MAME, and others have no problem. So, in a nutshell, do what you want, buyer beware, and always look out for number one, but don't step in number 2.
I have no idea what I just said. I'm low on blood sugar.