Quote -  How would you adjust your pricing if you were also asked to provide the source file for the image.

That is a tricky thing.  That could violate copyright and redistribution laws. If you were to provide a scene file to the person, they would have to have Poser and all of the items that you used in order to use that file.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi