Quoted from DaveH:Stern’s in the 4k range are a bargain. Metallica Pro, AC/DC Pro, Aerosmith Pro. That’s an amazing amount of pinball for the price. And the great part is, you can normally turn them around and get back what you paid. The worst you will do is lose a couple hundred on it in a year or two.
+1. You can find a lot of good Stern games for $4500 or less. They may not look the prettiest but most have a good set of rules and good gameplay.
For WPC games, Shadow, Fish Tales, and BSD are great games with challenging gameplay that won't get old fast. Prices are still relatively cheap but going up.