During his GDC 2013 keynote, former Diablo 3 Game Director Jay Wilson admitted that both real-money and in-game gold auction houses “really hurt the game.”
Before launch, Diablo 3 design team expected the auction houses to be used by a small percentage of players and that the number of items listed for sale would be limited. But soon after launch, the team learned that their assumptions couldn’t have been further from the truth. In fact, nearly all Diablo 3 players used either of the two auction houses at least once and more than 50% of the players use them regularly.
According to Wilson, Diablo 3 is still being played by 1 million players each day and 3 million unique players per month, so this should give you an idea of the number of auctions held and items sold each day.
Problem is, this made money a much higher motivator than the game’s original grand objective of slaying Diablo. Ultimately, the auction houses, and especially the in-game gold auction house, “damaged item rewards” and stirred gameplay focus from action to farming and trading.
"I think we would turn it off if we could," pondered Wilson. Unfortunately, this is not possible anymore since most of the players already use the auction houses and Blizzard "has no idea" how many players like the system or hate it.
In the end Wilson explained that the company doesn’t want to remove a feature used by a large number of players, but it is actively working on a viable solution that won’t be revealed now.