I have a slightly odd hobby. I really enjoy stamp collecting. 
Cool, you can also say you're into philately (a word for the study of stamps).
Oh I didn't realize it had an actual name. That's awesome. Do you know when stamps first started being used?
Well the word is derived from a French word and coined in 1864, so that far back at least. Probably a lot longer since mail has been around a while.
Yeah for sure. I'm trying to get a good collection of old and new. Do you know anything about the most expensive stamp ever?
There is a stamp called Inverted Jenny which is an error where an airplane is printed upside down. A single one was sold for $977,500.