About 3 years ago, I went to a show where I met John Higgins. After looking at the portfolio of art he had for sale, and being really impressed, I asked him if he could do a drawing for me at the show. Since he was from England, I didn’t want to take the chance of a more formal commission and slow turnaround time (if ever). He said he didn’t bring his tools with him, although he had them in his room. I offered to pay double his ordinary rate if he could do a Phantom Stranger commission for me, and offered to buy the paper, if he could do it before the show ended (pads were being sold there). He agreed, and I now own a great piece which he finished the next day. So, sometimes, artists will change their minds.
By the way, I have been singularly impressed with artists I have dealt with. I have a standing rule that if an artist finds that doing work on a piece takes longer than expected to get it right, I offer to pay more since I always want the artist’s best work. Not once has any artist taken me up on this offer.