My opinion may be slanted because I am a photog, but in a word, no.
I would think that if your FI's good friend makes a living at photography then you would need to pay for his travel as well as his photography fee.
would FI's friend be going to the wedding if he wasn't the photog?
you also need to consider how much work dw's are from a photogs stand point. Could FI's friend stay home that weekend and shoot another wedding? making the same amount of $.
just things to consider...
~ nic