Well, you don't get 50% for every purchase, that's only if you buy $200 worth. $100 is 35%, $50 is 20%, $20 is 10%, etc.
For those of you that don't want to use a CC, PP, or Skrill but you usually get game cards consider buying VISA or Mastercard gift cards. You can register them online and then use them like they were proper credit cards until you use up the prepaid amount.
Note that if you get one of these gift cards there's usually a $1-$2 activation fee that you pay at the checkout counter. So if you want to get a $50 gift card it would probably be around $52 dollars total.
I believe this can be purchased in many of the same places you get the game cards; Target, Wal Mart, etc.