It feels really dickish, and I was struggling to figure out exactly why. I thought about it and realized there's really not much difference between him rolling to sell an orchestrion roll and everyone else rolling for gear. Either way, your group is going to run the raids until everyone gets their drop.

Breaking it down, I feel like the difference between the rest of the people joining this group and the guy rolling to sell the orchestrion roll is

"Let's help each other out."
vs
"I'll help you out, but only if I get paid."

In both cases, all parties are getting something out of it, but one just comes off as a lot more sleazy.