Everyone wants this, but it is only because of the reason Zionia pointed out, you can only get about 1,000 creds a day from voting, however people want a lot more for spawners etc. so if this was available, especially at the rates you suggested, people would no longer be bothered to vote (unless really dedicated) and they would just try and sell their items for diamonds. At least if you can only get credits through voting then the staff know that any creds spent come from votes towards the server!