For all my prototype needs, standard cardstock (http://www.amazon.com/gp/product/B00006IDRW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) and a decent paper cutter (http://www.amazon.com/gp/product/B003SLAAOO/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1) will get you ~2000 cards worth of paper for ~$40. It also allows you to print your prototypes, which isn't really an option with blank playing cards.