Yeah, I don't see a reason to get worked up about this.

He's new and you're really giving him a rough time to say the least.
The guy did a clean, if non traditional build, had some buddies who were interested in buying it, and thought maybe he could make a bit of money selling them. What's the big deal?
It's stuff like this that makes some people not want to post their projects. I'm wrapping up a scratch build. It's my first cab, I came into it with virtually zero woodworking skills, and it does show a bit. I'm probably not gonna do a project thread. I think it's turning out ok, and I can take constructive criticism for sure, but it seems like when somebody does something non-traditional or something that's a bit rough around the edges, words like "crapmame", "lazy", and "stupid" start getting tossed about. I don't think everyone should just praise everything, as that benefits no one, but just offer some constructive criticism or don't say anything at all.
Anyway, in case the OP is still around and thinking about it, I'll respectfully add my two cents as to why this really isn't viable. Even with a very conservative cost estimate, say $100 for the X-Arcade, $150 for the TV, a $50 PC, $50 for the remaining materials, and a measly $50 for your labor, we're already at a $400 price tag.
Someone who wants an arcade unit will likely want a more traditional cab - which they can probably find in their local classifieds for less than $400.
Someone who wants a setup like this and does their homework will realize that they can pick up a tankstick for $100 and hook it up to a PC and TV that they probably already have.
If your buddies are willing to pay you to set one of these up for them rather than do the work themselves, I say go for it.

But it's probably not worth your time and money to start producing these and putting them on Craigslist or Kijiji or whatever.