I've used these, because I've had problems (who hasn't?) with K2's credit card service.
Used to be though it gave you gold according to the old formula, which wasn't a real bargain, but not a ripoff either (especially since I got a $10 surcharge added to the cost when I bought online, thanks to Moneybookers being in a foreign country).
But now apparently, a $15 card gives you 5000 gold and 4 mystery boxes, while a $30 card gives you 11000 gold and 6 mystery boxes.
(Thanks to AllyK/Delacourte for posting this)
Private Patch Server
3 days ago