I don't think that cab is an epic fail.
Did you see the double X arcade one?

Yeah, that one is pretty bad, but it almost had to be a customer request.
Personally, I think it looks like something that would sell well for $300-$350 flatpacked and assembled like ikea furniture.
Tons of people have asked for that.
I think the biggest shortcomings are these:
He's using the USB connector instead of PS2 on the x-arcade which means that there is a limit of 6 simultaneous inputs including directions. I'm sure this is the case since he says a USB keyboard is included and the x-arcade requires a PS2 keyboard to be plugged in for the PS2 output to work. If it had a PS2 keyboard connected, he wouldn't be including a wired USB one.
He's using Maximus Arcade - front end of noobs.
These two things make me think that he's someone who doesn't really know much about this stuff, but got their own rig running with an x-arcade and thought "Hey, I could make money off this!"
I have a friend who had that reaction to my first setup. He thought we would throw a cheap computer in every old cab we could get our hands on and put it up on ebay "with thousands of games included!" It took a while for it to sink in that it would be like selling a jukebox with thousands of bootleg songs downloaded off the internet.