My photographer is giving us a disk of all the high-res photos from the wedding for us to keep (and make our own copies of).

If your photographer doesn't charge much for the actual time to shoot the pictures, he probably relies on making his money through charging for the negatives. (If he didn't shoot with film, he doesn't have negatives, only an archive of the digital images.) I wouldn't mind paying extra for the engagement pics, I just wouldn't buy all 300. However, I definately wouldn't want to pay extra for each wedding day picture. You need to talk to him about this now *before* the wedding & try to come to a compromise that is fair to both parties.