I traded it for a TF2 item (earbuds) which I sold for cash. I'm *really* wary of selling things for cash because of the risk of being scammed and I normally use Steam trade which is safer. This is the first time I've traded TF2 stuff for cash. Overall I have probably traded ~$100 worth for Steam games.
Edit: I just did a quick check for CS:GO keys and they are going for about ~$12-15 now. I was lucky with getting a key really early.