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.
Wow! I don't think I will ever be able to afford anything quite like that hah! Is that the most unique stamp out there?
Well "invert errors," as they are called, are generally quite rare and highly valued.