Honestly, I think alot of this kind of thing is not for production as a saleable service, but more for the art and achievement factor.
But I guess there must be some clients that would appreciate this sort of work. Maybe that they would have so much control over the outcome of the picture, and still be scaleable?
I cant see myself putting enough time to learn the mesh tool like that, but I admire the knowledge. As someone said above, I bet they really learn a lot about composition and the nature of colour from this work.