This article is from the Pinball FAQ, by Andy Oakland sao@REMOVETOREPLY.mit.edu with numerous contributions by others.
Games available for home purchase fall into three categories: Used electro-
mechanical, used solid-state, and new (all new games are solid-state). Which
is right for you depends on what you want, how much you're willing to spend,
and whether you ever intend to sell or trade the game.
Think a bit about why you want a game. If you want it to play, chances
are that you want a solid-state game. They play faster, and the software
has features that could take you some time to uncover.
If you're looking for something to tear apart, down to the bare wood, and
build back up again (only better), buy an electro-mechanical. Doing the
fix-up on a solid-state game wouldn't be as fruitful--At some point,
you'd be staring at an IC-laden circuit board, and that's way beyond
cleaning contacts and tightening springs.
Aside from knowing why you want a game, you should zero in on which game you
want. The market is fat with choices, and there is a fair chance that,
if you look in the right places, you can eventually find what you want. But
you can't go into the market saying, "Oh, just find me something you think
I'll like." It goes deeper than issues of color and whitewalls or no: You
will fare best if you have a wish list of games you are interested in.
How much will it cost? It depends on the popularity and rarity of the
game, the condition of this particular machine, and whether or not you live
in California. (Not a joke ... Prices run higher in The Golden State!)
A semi-functional older solid-state machine can be had for as little as
$100, while a new game fresh from the factory runs about $3500. Typical
price for a game that's seen a couple years of use would be $400-$1000.
An electro-mechanical game can run anywhere from $150 to $750, with
real collector's items (like Humpty Dumpty) significantly more.
If this is your first machine, it's highly recommended that you get a working
one! Picking up a cheap junker may be tempting, but you'll never get it
going without experience, specialized equipment, and a stock of spare parts.
Try to buy from someone who'll deliver it in working condition, and stand
behind it for a while. Ask for references!