dedulya37,
I have not once encountered such. That's right.
But I think that this is not very correct behavior of the artist. He has such a profession - to create masterpieces that sell them. If it is, of course, part-time customs officer did not (Rousseau). Or a stockbroker (Gauguin).
In short, if it is a profession, not a hobby - it is necessary to write and sell. And so that does not erase the memory of creativity - is now seamlessly take pictures and even make copies, both on paper and on canvas. Similarities, especially in the case of on-wet watercolor, is such that I was forced to sign the word "copy" to avoid confusion
With work, for the artist's emblematic, for example, we are doing so: we sell, but with the obligation to provide for individual exhibitions. Also the normal version.