I’m curious—why are museum professionals astonished that an artist might
want to be paid for the display of his/her work?  Does the museum agree not
to charge an entrance fee when the artist is not paid?  The museum has
expenses to meet, right?  The artist doesn’t?  Who pays his/the artist’s
rent?  health insurance? for materials, research?  The museum gives the
artist exposure?  Where would it be without artists? Needless to say
(maybe) is that the exhibition of contemporary art (and the livelihood of
its curators) depends entirely on the work product of artists. 

I’m in complete sympathy with the dilemma faced by museum professionals who
read the dismal salary surveys, but those salaries normally come with
health insurance, vacation, sick time—perhaps even a sabbatical.  The next
time you’re thinking about telling artists—not Rauschenberg or Stella, but
most of the rest—that they  should provide the content of your exhibition
for free, you might consider asking them exactly how much THEY made last
year. . . .
Jim O'Connor