I am guessing, but I assume that some museums pay market rate for art work so that they won't be accused of gouging artists for the privilege of bragging rights that they are in a prominent museum. I am also guessing that some museums, and corporate art buyers also, do underpay with the implied cachet making up for the discounted price.
Thanks for such interesting report about SAM . Also there some artists that they don't know how to put hangers,wire on their paintings and probably they will care less about Art Museum Operations except a few .