I guess what I meant by "Professional" was not so much that the musician got paid for it, but that someone who plays bluegrass has the talent and dedication to be a professional. Most of them don't make a living at it because, well--how do you get a folk musician off your porch? You pay him for the pizza. You get my drift.
The point I was trying to make before was that even though bluegrass and old time music share a lot of songs and instruments in common, bluegrass is much more difficult to play. This is because (on banjo anyway) the picking is at least double the speed of the melody. If the melody is basically a combination of quarter and eighth notes, the banjo is picking sixteenth notes. In old time music, the banjo would be playing mostly just the melody notes (or just stumming chords for backup). Please correct me if I'm wrong, I want to understand this better too.