I have a Batman Forever.  I believe a Batman Forever in excellent condition is worth between $2500 and $4 grand. There have been a few for sale, but real figures are hard to come by.

The dot-matrix display is worth apx $425 to replace, but is seldom in need of repair or replacement. The cable running to it can be upgraded or purchased for $20 from Marco Spec etc.

Batman Forever is very collectable and is a widebody. The cabinet, playfield and translite are stunning to look at. The dot-matrix displays are second to none and ofcourse huge being the largest dot-matrix available on a Data East. There were apx 2500 machines made only.
The game is fun, and makes u work for the missions. It is very much like Indiana Jones in the overall game speed/style. Prices vary between $2500 starting and $4,000 for a mint one. This game is 100 percent eye candy. I have a Australian delivered machine which is number 2452 out of 2500 made.

I paid $2500 for a HUO one owner machine 2 years ago, and I consider I got mine for a absolute bargain. The owner imported it from the USA new. Mine is like new out of a box. I was very very lucky. Thats the only pricing I can give you to help u make a decision on what pricing u feel a Batman Forever would be worth today. I scored mine at the peak of the global financial crisis. Play one which has been shopped properly, or just a low usage game, and u shld be impressed.

Hope it helps.