Curious about Zazzle Buyers *

Ok, so what makes a person buy a single postcard on Zazzle, or one card? Are they grouping their purchases, buying one card here and there, to make the product price more than the shipping cost? I've gotten orders for single postcards, as well as multiple, but wonder who is buying just one? I guess if you can't get to a particular city, but you'd like to send a postcard with that subject, a site like Zazzle is the ticket. Most of my city cards or postcards sales are from over seas locations. Are these other Zazzle sellers shopping around the site? Where should I start marketing my store with all this in mind? Questions, questions, questions. If anyone out there has any insight, i'm all ears. And now, on with producing more products. :)