I didn’t know what I was doing for the first book I ghostwrote and charged in the mid-four figures. But it was an easy project, so my compensation worked out okay.
My second ghostwriting experience was much more involved, and I charged twice as much. The fees for that book turned out okay, as well.
I understand that the minimum going rate for an experienced ghostwriter is $15,000, with established ghostwriters in the $25 to $35,000 range. (And I’ve heard of much higher numbers too.)
As a means of comparison, Book In A Box, now called Scribe, is a business that offers a turnkey solution to authors. Scribe will ghostwrite, edit, and publish a nonfiction book for $36,000. They may effectively be your competition.