Originally Posted by OC'ing Noob
You don't seem to be getting this... any "economy" created by 3rd party websites will have no bearing on the actual game. This 3rd party created economy that you speak of has nothing to do with the game but is rather a black market which comes with inherent risks. Anyone with even half a brain should know this. If one does not get that concept, he should not play the game or use said sites. As for PvP, I will believe it when I see it.
The third party market has a HUGE effect on the economy... Diablo 2 patched in the "diablo clone" event purely to deal with massive amounts of a ring being sold on third party sites.
People will spend around the same amount of real $$ on the game as they did before. Item shops will probably start selling items more now, instead of just gold... since those come from bots, it only takes until the person who bought it from the item site decides to upgrade and sells the item for it to enter the normal economy.
In the end, the "third party" items will enter the mainstream economy and still have a huge effect on it. Just look at Diablo 2- most players never even found a real high rune themselves... they only traded for them. That was possible since they were botted or duped by item shops, then the people who got them there eventually trade in game (or onto jsp, then in game). The exact same thing will happen (and is happening now anyways) with Diablo 3.