Kath, there are 'fringe' sessions and there are 'official', free sessions. I suspect that the less confident players go to the advertised 'official' sessions, and the little gangs of friends set up their own sessions which may seem more exclusive.

What I noticed, this year and last (under the new management) was the lack of stewards with collecting tins in the 'official' sessions, though the stewards were active at the workshops, dances and concerts, collecting dues from those who didn't buy a weeks ticket.
As a festival that is so spread around town it makes sense for some people to pay for seperate workshops, though we get good value from the season ticket and enjoy the sessions too.