Hmmm... as an anthropologist, I would distinguish between SCA folks and Pagans by asking- is this a religious activity? Religion is certainly in its own category of human behavior as opposed to line-dancing and other hobbies.
It seems a little odd to put Pagan practices in with line-dancing and SCA, while not putting all other religions into that same category, since most religions have distinctive dress. When I go to my Episcopalian church on Sundays, the priests are wearing robes. Are they playing dress up? Or is that just the time-honored appropriate dress for that particular religion? When I put on a cross, is that the same action as putting on any other necklace? It is the perceived sacredness of the items, or their association with sacred activity, that is distinctive.
Furthermore, I know an awful lot of Pagans that do not dress up any different from usual to do ceremony, so I'd hesitate to make dressing up in robes the most salient feature of Paganism. I am myself a Druid (and a Christian) and while I have a robe, it rarely gets worn. It is just not practical (for me) to go hiking five miles to my grove (up in the mountains) in a robe. Nope, I'm always doing ceremony in jeans and tank-tops. LOL Plus, a lot of Pagans prefer nakedness for ritual when they can safely accommodate that- there are a number of reasons this is the case.
In my opinion, when I look at world religions, the various Pagan religions are just different takes on the same human behavior. All religions have some basic elements of human behavior and thought in common, which sets them apart from the mundane and makes them a unique area of study. We might initially find some of the newer or less commonplace religions different and strange, but ultimately if you look at the elements (ritual, sacred stuff and places, meditation, magic, worship/prayer, some sort of expert like priests or shamans, etc.) they're all kind of the same underneath the surface. Possible wild cards that are a bit different are Theravada Buddhism and Confucianism, but the rest are quite similar. The more I've studied religion and human behavior, the more the idea is driven home in my head that there is something ingrained in most people to have this type of behavior that takes part of their life (more or less) and makes it sacred in some way, and generally this deals with divinity in some way. This journey comes out in different clothing, ritual, sacred objects and places, experts, ideas about divinity, etc. based on culture. But underneath those cultural differences, it is, like many other areas of human behavior (having family and social groups, politics/government, etc.) pretty much the same behavior.