World of Warcraft: Warlods of Draenor pre-purchasing is open now including a free level 90 character booster. The booster is now available as a standalone purchase should you wish to buy it without the expansion.
We've got a list of the expansion's pre-purchase options, including different versions and contents here, ranging from £34.99/$49.9 to £49.99/$69.99.
Blizzard has now put the booster on sale via Battle.net at £40, and has explained how it works in this new trailer:
It follows claims from Blizzard that the booster costs so much as not to devalue the levelling effort.