I usually buy postcards of places I am going to visit before I get to the destination. Zazzle is the only webstore I know that has them, but I am sure there are others. The pre-trip purchase gives me more time to see the actual sites when I arrive at my destination and not wander around looking for a souvenir store to buy postcards. The postage is really the big cost overseas. To mail a postcard to the U.S. from Scandinavia costs $1.50 to $2.00. In Europe it is usually a $1.
I have about 32 friends on my postcard list, so I can address them ahead of time, which leaves only the stamp and short message to complete the process. In this age of email you would be surprised how much people enjoy receiving a postcard of a far off place with a strange looking stamp on it, and a shoes on the ground opinion of the place.
About the print:
One complaint I have with Zazzle is that they usually send me one card that is in portrait mode when it should be in landscape mode. When I went to Spain I sent 8 (same picture) of the 32 back. For Malta there were no errors. This time it was only one of the 32. So it is improving.
Also, many of the "modern" postcards of popular tourist sites are from 10 or 20 years ago. Some fresher stock would be appreciated. And more variety is always welcome.