AldoManutio, I don't see how what you says conflicts with what I say. The artists own the copyright. Thus they can

1) show their work off under a CC non-commercial attribution license.
2) issue themselves - or the person they are working together with - another license, that allows commercial use?

I still don't see why using a CC NC BY license would prevent an artist of using his own work for commercial purposes. (Or allowing other, specific persons to do so.)