Yeah, if you're sending the game, you have to pay for shipping. Just get a cheap food scale (or spend a bit more and buy a postal scale on ebay). The above poster was right, in a padded envelope most games are 5-6 ounces.
I've not sent out a game since goozex started offering the labels direct through site. I was using paypal shipping before and most games were $2.20 or so to ship out. But it sounds like the goozex is a bit more, so use the paypal link given above. You can use it for anything you ship, goozex or otherwise.