Once we established that it was pretty easy to see how letting his rate float up would help with his workload, he would not only be less overloaded but he would be collecting more of the market value of his work. Since in his case (he's nominally retired) not working at all was just fine, he had a lot of freedom in over shooting the market and then coming back.
I recognize that its not as useful for someone who is wondering where rent money will come from.