20. Model Trains
For people who assemble model trains, they take it very seriously. They spend years putting together their little villages and collecting accessories to go along with the train sets. Even celebrities like Rod Stewart, Gary Coleman, Frank Sinatra, Elton John, and Walt Disney all collected trains.
While browsing eBay, I came across a Brass HO Overload EMD GP-35 which sold for $5,100. And another sale of Challenger Imports sold for $7,500. It seems like model trains regularly sell for thousands of dollars. However, like most collectibles, you need to do some research to understand the value of each train set and individual piece.