Clearly, I don't work with models. I'd never heard of this before. Although the therapy dogs I shot all had their own cards, baseball card size, with their pictures on the front, and bios on the back.
Back to your original question...For the therapy dogs, IIRC, I charged them $40 for the (simple) layout, then doubled what mpix was charging me for printing. I was using images from a shoot that I charged for separately (the therapy dog org paid for the shoot, but I kept the license for the images).
I figiured I would just stick $100 on top of what the cards cost to print and ship. We shall see what happens! Thanks Ann!!
That seems reasonable. I didn't want to charge the dog owners much because therapy dogs work for free. Your situation is different.
Tell them the "usual" charge is $200 but because they're booking as a group and it's their first time you'll give them a discount ... if they like your work they could be back or refer their friends ...
Here's something I wanted to share still. If you want some quick interesting results, I recommend TychPanel for Photoshop (or any similar tools that allow you to create diptychs easily). It saves me a lot of time on similar projects.