If your jumping right in and looking at spending 7k+, my advice is get out and play. Find some beercades, bars, game rooms, or any machine anywhere. Find what you like. Dont go on what people say is the best or a must have. If you like metallica, acdc, or rock bands in general, start looking there. Plenty of movie, TV, comic book themes to look at also. With the price range you are willing to start with, there isnt too many games out of your budget.
Next, find a trust worthy tech. This is where playing out in the wild really helps. Start talking with people. See who is the go to guy in your area. See who people say who you need to avoid.
Good luck. Pins can be very addictive.
I wouldn't count on any game holding its value or going up anymore. If you can pick up a new game, beat on it for a couple months, then move on to something else and only lose a few hundred, I think that's a win.