Showing a sketch for approval is a larger job and often requires payment in thirds from me. Revisions are limited before extra charges are incurred. It takes a lot more spoons and I'm not always up for it.
If I am getting commission art, I have to understand that I am getting the artist’s interpretation of my request. If I need more control over the final piece, the artist and I should negotiate details and price before work begins. Changes are new work, they should be paid accordingly.