One recipe for a bargain pinball machine is great game play with an unpopular theme. One great example of this is Johnny Mnemonic. I struggle to think of another machine that can match the thrilling speed and flow of Johnny Mnemonic but the movie was a bomb at the box office. Someone has actually taken the effort to retheme it to The Matrix movies and it looks fantastic. It's easy to imagine that Johnny Mnemonic rethemed to The Matrix could fetch very high prices. Alas, it is a one-off and not for sale.

Another recipe for a bargain pinball machine is an acceptable theme, but with some flaw in the game play. Roadshow is a good example of this. The linear mode progression is something that can be irritating to some home environment players, as it has apparently irritated you.

The following list is a combination of both of the above and I think is a great starting point for bargain shopping. The prices are woefully out of date, but the sentiment is still true: http://gameroomblog.com/guides/the-top-ten-best-bargains-in-pinball-today

A summary of that list:
10 - Classic Sterns
9 - Johnny Mnemonic
8 - Demolition Man
7 - Jackbot
6 - Fish Tales
5 - Tales From the Crypt
4 - Judge Dredd
4 - Revenge From Mars
3 - Road Show
2 - Bram Stoker's Dracula
1 - Shadow

There's never a substitute for playing a game, but I found this Kindle book (from the same author of that blog) to be a useful reference, especially for pointing out game play flaws which are impossible to determine from casual play: http://www.amazon.com/Pinball-Book-Guide-Classic-Machines-ebook/dp/B009KZCR7U

The Matrix pinball: