I am sure he knows it helped him gain exposure and fame as do most of the fighters who have been on the show. Just like Franklin most tuffers have talked about how they would not want to do the show again.
If you had an internship with Microsoft and parlayed that into a high paying executive position would you want to take an internship again if Microsoft asked just because that is how you got your foot in the door in the first place?
Franklin took advantage of his opportunity by winning fights and drawing in a large fanbase which in turn has also helped the UFC. He won many of those fights for relatively small amounts of money so he has paid his dues. Regardless he is still doing the show but he is acknowledging the pay is low and it is not really a beneficial opportunity at this point.