I think this is largely up to you, as you have to determine what your work is worth. You also have to take in consideration whether or not the website will be profiting off your photo or not. But honestly, if it was me... I'd be trying to work this in a way that works out best for you to market yourself for future business. For example: I'd be willing to let him use the photo on that one website for free, so long as he provided a hard link back to your website (or referenced your company if you don't have a website).
And I'd try to get a deal where they use you as their official photographer for their paintball events (which you could charge your standard fees for), and in return you grant them non-exclusive license to the photos you take of their events. Something like this gets your name out there and gets you more business. Of course if you're not located in their area then this won't work and you'll just have to work out something in exchange for that one pic.