You guys are forgetting the fact that you won't be able to buy Tibia Coins with Debit/Credit Cards or Paypal for the first 6 months.
I think they made an exception with Brazil though.For some payment methods, though, it will take 6 months until your Tibia Coins become transferable. These payment methods will be marked with two asterisks in the Webshop.
Anyway, in the beginning there'll be a high supply (people already stocking scrolls) but as time goes there'll be less tibia coins to buy, hence price will go up. Until we reach the 6 month mark.
Edit: You can buy them, you can't just transfer them in game.