Perhaps the amount isn’t important per se to the artist, but it is important because of what it means to the payer.
The artist gives what he values most, his craft; in return, he wants what the buyer values most, his money. In that fashion, and not through words which are empty to the buyer, the latter must show the former respect. And respect matters most.
With a fellow artist, the trade is in recognition and genuine prise.
Maybe the heart and head are not so different after all.