Section 2.2 of the terms of service reads...

Real Money Trading, Farming and Power-Leveling. You may not sell, purchase or exchange for real-world money or value any in-game currency, accounts, characters, in-game services, or in-game virtual items. You may not play the Game for the purpose of acquiring virtual items or advancement in game play on behalf of a third-party or for the purpose of selling any virtual assets to a third party for real-world money, specifically including "gold-farming" and power-leveling services.

Yet real money traders in the party finder menu run rampant, selling completed runs of current content, including savage and ultimate. This is not enforced at all and no accounts have been banned or punished as a result of this.