I'll preface this by saying that no, I don't have $10,000 or thereabouts to drop on a machine, so I personally have no skin in the game. I really do enjoy MM; from what I've played of it, it's a great game. Good modes, good art, good toys.
I would personally probably be willing to pay $7,000 for one if it came along and I had the money burning a hole in my pocket. Before everyone says, "Guy's out to lunch; they'll never sell that low," hear me out. There is a way that I came up with that number, and it's not just me undercutting the asking value or saying "what it should be".
I think MM is that good of a game; complete package and everything. I'd be more comfortable spending $7,000 on a MM than a new Transformers LE or Wizard of Oz that I'd never played before. With that said, above and beyond a certain point seems to me to be a cachet thing. That's 100 percent fine; I know within the pin community, if I walk into someone's basement and see a MM, a certain bit of respectful head-nodding will go on, and I have no problem with that.
My personal issue, and how I came up with the price, is that I don't think I'm going to get as much enjoyment out of a $10,000 MM as a showpiece as I would any other three A- or B-list pins that provide me with an entire, solid collection. For that kind of money, I'm pretty sure I could get my choice of a TSPP, TZ, AFM, SM, whatever; any three or four games, and if I shopped right, maybe have enough left over for some oddball piece I want like a Gorgar. For $7,000, I can comfortably say, "Yeah, I'd drop that money for the showpiece, knowing full well it's nearly twice what any other machine is going for", without saying, "Yeah, that's too much money." Above that point, I can start drawing a hard line where I say, "I really like MM, but am comfortable having three A-list games instead of THE A-list game." Just my two cents; take it for what it's worth.