WoW korea just added a 100% exp boost potion that costs ~0.93 USD, and lasts for one hour. I think this is pretty interesting, personally, but I won't say anything else either way. Take a look at this next link though...describes how it would be the best move for them given their revenue has dropped by 53% in the last 7 months.
http://www.superdataresearch.com/blo...otransactions/