As far as GW goes I believe the sculptors are paid a flat salary and do not get a commission of sales, but I could be wrong.
I certainly hope they're not strictly commission based. The rules play too much into the sales, and the sculptors have no control over the rules. Just look at the Pyrovore; great model, **** rules, so no one ever bought one.
Give a man fire, and you keep him warm for a night.
Set a man on fire, and you keep him warm for the rest of his life.