So I thought I'd do that. I got into the beta and started to get some cards. Now, each game drops a limited amount of cards. If there are 8 total cards in the set you can only get four cards. You have to get cards from another game and trade with other people to get a total set. I decided that was a little much for me. Trying to find people who have the cards I want and finding a time that we can both trade didn't seem worth it.
So then what? I could just give the cards away, but then I realized that I could sell them on the marketplace. Figured I'd see if I could get a few pennies for them. Then I saw that they were being sold for around 50 cents each. I can't sell my real trading cards for that much. Sold off everything and ended up with a little more than $19 steam credit.
I got paid for playing games. That means that I'm pro now. I'm also totally set for the next big Steam sale that should be showing up in a week or so.