There is a difference between worth and value in my opinion. A machine is worth what what you are willing to pay and you be totally comfortable in making that purchase. A machines value can be determined by many things, the more modern generally makes it more valuable especially of recent the LE's. Many popular Bally / Williams of the 90's still hold good value but some are over-rated but depends on personal taste really. Personally I don't like The Addams Family and think it is not good value. Some machines have a high value because of the theme, the designer or because of it's rarity (small numbers) and I am sure many other aspects as well.
Check out the Pinball Database if you haven't already and of the Solid State machines many of the 90's dmd's will be in the top of the list with probably the top 10 sitting between $4000 to $10000 for a good quality one.
http://www.ipdb.org/lists.cgi?puid=29684&browser=1334484217&list=top300When you are talking dollars:
EM's probably low hundreds to $1500 for a very good machine
Early SS high hundreds to mid to high 1 thousands for a good machine
DMD of the 90's may if lucky under a thousand for a working project that may need some cleaning up and ramps etc up to $10k for a good machine
2000's Stern DMD - many holding a value of $3k and then going up
Having been in your position of first machine being a em that needs work and then wanting to get a working machine - make sure you do just that buy a working machine but maybe one that needs decals and new ramps one day as that way you can play now and do up later. And pick a theme that you like and enjoy.
