Ive done a group buy with Wizards before, I got about 20% off most stuff.
But arranging them is a bit of a ballache TBH as people are forever saying they want stuff and then dont come up with the cash etc.
Anyway I think group buys might fall foul of the rules on here as it would be classed as if I was trading on behalf of wizards if I did another one so I dont think I am allowed to do it here anyway.
If I am I would only do so if people paid 100% of the money up front, I wouldnt do it on a deposits basis again as Ive been too mess around in the past.