We all have reality TV like Pawn Stars and the two dingle berries from American Pickers to thank. Ebay and the misconception of "well it's selling for $X on Ebay" so mine has to be worth that much. We also have the increase in retail stores to thank.
Problem is that the guy who has had a Dr. Who in his basement for 10 years has no clue the difference between his machine and that fully shopped out and restored machine on Ebay or in a store for $5500.
Price guides like Mr.Pinball mean absolutely nothing to these people because Ebay is their price guide. Problem is neither Mr.Pinball nor Ebay writing a check for any of these games.
Subjective condition of a game is king too. What one might call excellent condition is fair to good in a collector's eye.