This is my second extension from anteprimasas. I purchased their reward points for virtuemart, then I asked them how to setup a credit system like fotolia and they developed this one! It is different from a pay with points payment, it splits the webstore in two parts: 'special' products to buy credits and products to be purchased with credits - using the same virtuemart cart and the same virtuemart payment system. I sell social music libraries, users upload their music and customers purchase with credits - and they can purchase credits from stocks of 50 credits each time. This is quite usual when you sell services, images, mp3s, videos, even coupons. This extension seems to be perfect for that.