We've had our Keurig since last Christmas and a friend told me about this site:
http://www.my-cap.com/?referrer=bing...gn=my-kap-caps They are little plastic caps you use on either cups you buy from them or old ones that you clean out. It is a bit of a pain cleaning the cups out, but saves a lot of $$. When we got ours it was about $12 for 9 caps and a brush to clean out the cups. Have you tried
http://www.greenmountaincoffee.com/ ? They have pretty good deals. However our local Jiffy Mart gas station sells boxes of 24 for $12.99, so we get them there now. Love the convenience.