Here's an idea that will make your current players ecstatic, increase the fun and quality of your game, keep people playing longer and make you all a ton of cash! "AUCTION HOUSE!" Give players something to do with those cards eating up their precious inventory space, a way to get the cards they want, and a way for the "free to players" to compete and work for the "pay to winners" at the same time. All for your in-game currency, just keep the commission reasonable, the more reasonable, the more players you'll not have thinking you are a bunch of greedy assholes, and the more popular your game will be, and in the long run making you more cash. You would obliterate all other "Card Games" out there, and you could actually call this a "TRADING" Card Game" which is where all of these so-called "Card Games" got their inspiration in the first place!