It worked largely pretty well to keep out the trolls; as it turns out, a very low amount of people bother trying to troll others when it means that they get hit with an account ban and signing up again means paying the entry fee again.
You could probably also see it as the reason that while SA culture is uh... pretty toxic, it still largely managed to be fairly consistent and polite to each other (towards other communities... less so). Take away the 10$ signup fee and what you get instead is 4chan (whose original culture was a wholesale copy of SA at the time, since it was made for SA users after moot got banned from SA).