#10 - July 28, 2010, 6:13 p.m.
You're more than welcome to purchase items from the Auction House and then relist them for a higher price; this is not considered "manipulating the economy" in any official sense. Please be aware, however, that this can be a gamble, and players may refuse to purchase the item at inflated prices. Account actions surrounding economy abuse are typically related to more heinous and obviously illegitimate activities such as real money trading (a.k.a. gold sales).