The way printers have cut costs on printing 4 over 4, or full color on both sides, is by ganging up the work. You send in your job and they print it with a bunch of other jobs and then cut everything up into card sizes.
The advantage of this is obvious, huge cost savings. The disadvantage is no press check, so your file has to be right because you can't adjust the color on press. Also you usually have to adhere to pretty strict rules to be sure file comes out correctly. Another disadvantage is no spot color or spot varnish, just CMYK with an aqueous coating to protect the printing.
I personally have a couple printers I use for this kind of work. They've always worked well for me. The first is Molding Box and I talk to Matt. They're local and it's nice to know your printer in person. The other one I've used is is Modern Postcard. Bigger and more strict but they have their advantages too.
Here's a couple of pieces I've done recently.
|This was a handout at a car show.|
|This was actually a bit more complicated because it had some scratch to win boxes on the back.|
It was printed at Rastar with the help of Kae Lynne.