Found this article which goes through a good analysis of how to approach this problem.
Why you must sell digital files, and how to price them properly
I would take in consideration the processing time, your education time, your field time, and the value of all that. I would have a contract that limits their use of the image. They can not post it anywhere, have any commercial use nor share it. Any of those would be litigation for damages.
So my question is, since this is a business, what is their intended usage? From there I would start thinking about pricing structure and a contract.
Just my 2 cents.
