It's messed up how some bicycle shops will refuse to make wheels, or even if they're willing - charge a ridiculous amount...
Just as a FYI, you can get awesome double walled rims starting at $30 and building a wheel should be about $25 labor & $20 for (standard) spokes... while this means that while the Worksman wheel may still be the best deal around, there's no reason why they couldn't build ya a nice wheel - they were just scared 'cause it's a MB, so jus' don't tell them. What they don't know wont hurt yer wallet
Here's some sweet double walled rims if yer curious;
Bikeman: Alex DM18 26 36H Black Mountain Rim
Bikeman: Alex Adventurer 26 36H Black Mountain Rim
Bikeman: Sun Rhynolite 26'' Rim, 36h PV 559 ISO Black
That's an awesome shop BTW, they really dig motorized bicycles & take pride in their work. They'll build ya a wheel for the above prices... but after S&H I dunno if you'll save any cash *shrug*