Not arrogance, but intelligence.

If we give away our work, or for little money, we devalue it.

MINIMUM $100.00, I would stick closer to between 250.00 - 300.00

Does he anticipate how many copies of the book he wants the license purchase to cover?

And spell out the limited use of the image and how many copies he is limited to producing. If its 250 books, etc. He will have to re-purchase rights for any books above that number which allows him to keep his cost down and if his book is doing well, he can pay for another round of usage.

If he wants unlimited use of your picture, the price goes up.

Way up.

Roman