I haven't heard of a play-card identifying sensor before. Sensing the red/black colour is easy. There is colour sensors that can do this for you. I know that TAOS makes some and I have some lying around somewhere, that I haven't had the time to play with yet. Or you can shine a red light on the suit-icon and see how much light is reflected. The red suits will reflect more light than the black ones.
Identifying the specific suit is harder. Maybe some sort of scanner, like a normal flatbed scanner for a computer, with a narrow light sensor can be used to scan the card and the microprocessor can then identify the card from the image.
It's hard to say anything about cost, before you have chosen a strategy.
Good luck and please remember to post any progress here. It's an interesting task and I'd like to hear how you progress.