I love, love the artistry and feel of the old electromagnetic pinball machines. I didn't know that they were relatively cheap, though - I would have thought quite the opposite, what with (slowly) increasing demand and a dwindling supply (as they end up in the hands of people with Permanent Collections).
A game like the one i'm posing by runs anywhere from $1500-2000 for a lovingly restored machine.. The current games are $4500-6000.
For gameplay, though, I generally like the newer machines. Oh, lord, don't get me started on pinball. I just erased like five rambling, gushy sentences about my favorite machines that pretty much no one in the history of ever would want to read.
I think you answered the question why the older machines are relatively cheap. Most people prefer the gameplay to the newer models. If all things were equal I actually prefer the simple older machines, but in spite of being restored, they lack umph. No amount of restoration can put it back in i'm afraid. The later models have a million things going on, ramps, tunnels, 3-4-5 balls at the same time. It's overwhelming. Just hit the ball anywhere and you're gonna get something. They are a lot of fun too, but there's something about those classic machines I just love. It's what I grew up with I guess, but the bumpers are dead. The new machines are lightning fast.
I spent most of a Saturday evening getting my ass handed to me by this Dolly Bird...

That's
Cirqus Voltaire we are playing
~Paul