Also, Craigslist is a great way to expand your collection. A set like Grand Central costs $50 new, but you can easily buy an entire collection of 5 or more combined sets on craigslist for $100. Typically people sell these sets as their child grows out of them so there is always a good used supply. Geotrax is very durable so used sets tend to work just fine (although obviously they will be missing some of the little pieces).