The Festival of 1000 Bikes has more than 1000 people paying, on average, about £60 for two sessions (some pay for three, some only pay for one). The 'trackday' part of the business can't fail to be making money.
However, they put on a lot of other activities over the weekend as well, many of which will cost them money, and because of the vast number of participants there's a lot more off-track marshalling to be done.
Then there's the thing the punters pay to get in to attend; club stands, traders stalls, etc. I would think that should break even as the traders presumably pay to be there.
Which brings us to the issue of the celebrities booked in to boost numbers through the turnstiles. Someone somewhere must have thought it made a difference to attendance, but I think they ended up with two different events (maybe three) at the same venue on the same weekend; the trackday, the clubs 'exhibition' and the chance to meet celebs.
I stopped going because I got fed up with not being able to camp somewhere flat and grassy because everyone and his dog seemed to have already got in before the gates officially opened; they oversold the event and then didn't manage the space they had available.
Other people manage to run combined classic race / classic trackday / classic exhibition weekends (both in Europe and here in the UK) and still make a profit so it can't be that difficult.