I managed to pick up a 1991 Data East TMNT machine for 500$ a few auctions ago. Part of the Dot Matrix Display is out, but if you can live with that, it was a great steal for 500$. They had some particularly crappy ones (both in condition and "fun-ness" go for much more).
The key to pins is that the serious pinheads kind of frown upon certain makes (DataEast and Gottlib in particular) because they tend to have smaller rulesets and are themed. With the exception of Guns&Roses, Rocky & Bullwinkle, and StarWars, the rest tend to go from much less then an equivalent year/condition/feature williams or stern machine.
I personally like the DE machines myself.