I would prefer the paid per style, because you could easily be ripped off by people gaining access to all styles for a small fee, downloading them all and then cancelling. Even if they cancel, not getting further updates wouldn't bother them too much, depending on the person of course.
That's why I wanted feedback . I had my doubts about such, but wanted to know everyone elses thoughts before proceeding to do such.
The idea is nice and I do agree, it would be easy to take advantage of, though, with no updates, updating vBulletin would be a bit harder since some things would be missing .
I will keep the point in mind as I further develop the styles.