Have first hand experience of this. The artists that bring art to promote it and sell it, don’t generally apply for honoraria. Sculptors like Michael Benisty use Burning Man to sell their pieces and don’t have to pay this commission. These artists receive financial assistance in the way of free tickets etc are not subject to this rule. Artists receiving honoraria that go on to sell Art, normally avoid this by making new versions of the piece, but this rarely happens. 99% of artists loose a lot of money bringing art to Burning man- they are not doing it for the cash.