We just sent this postcard out to our current clients are the call are rolling in. It offers a buy one at full price-- get the second for 50% off. Yes, it sounds like a huge deal. But do the math. You're really not giving away too much. The big idea here is you're inspiring them to get more than just one service done at a time.
***About the PSD files*** For the absolute best looking postcard, I highly suggest Photoshop Elements. This is the easiest and best way to get a quality final postcard. However, Publisher can work somewhat decently if you are printing on your own computer.