Thank you for your comments, Akatsukami!
Gunduzahar is a profitable venture, unusually so for the Blue Mountains at this time in Middle-earth's history. With two kindreds of Dwarves (Firebeards and Broadbeams) working over the mountains for three Ages of the world, I expect most of the riches were found long ago, and the smaller lodes worked out. This is why I've put the rich pickings near the sea, which Dwarves normally avoid.
The copper and other minerals coming out of Gunduzahar itself are profitable, but the real wealth comes from Veylin's prospecting for gems, which is why he keeps fretting that he doesn't get to do more of it.
As for Grimr's pay and perqs, he is benefitting from the fact that Veylin is an unusually generous Dwarf. "Your hands will flow with gold, but over you gold will have no dominion." Such a softie.