Most expensive collection: $15.2 million
As with every collection, the condition of your stamps is directly tied to its worth on the open market. Take the case of a 158-year-old Canadian stamp sold at a New York auction last year. In a tarnished state, the rare "Twelve Penny Black" would simply be an impressive keepsake for collectors, maybe able to fetch a few thousand bucks. But this print of Canada's most famous stamp — which features a portrait of the young Queen Victoria — was in such "extraordinary condition," according to the Winnipeg Free Press, that it cost a private bidder $260,000. That may sound like a lot, but it's nothing compared to the most expensive stamp collection ever sold, hawked in 1993 and currently valued at $15.2 million.