They are really hard to find in nice, unrestored condition. The game was so good that they seemed to get played to hell on route. The unrestored ones I've seen usually have planking, or a good amount of playfield wear, or a bubbling topper, or a faded cab on one or more sides. None of those are easily fixed. Nice toppers are crazy expensive and rare. The nice silkscreened decals from Phoenix Arcade are long gone too. I don't think I'll ever sell mine.
I get what Snyper2099 is saying but I'm not one of those guys who plays solely for points, or solely for "winning" the game. My play-style tends to be to work up the raft levels and all the while trying to maximize my points depending on the oportunities presented, and if I'm lucky complete vacation planner along the way. I don't get into the drudgery of always trying to complete the River letters in a methodical way, or always trying to set up 5x jackpots. It's just not fun to play that way. So, it never really gets old for me. Go with the flow! It's more fun to play that way.