I've done the trip with the Lotus Se7en club and agree that the cost is high. Personally I'm not interested in the live band etc and not interested in the overnight stop en route. They take one or two large vans needed to carry the huge marquee, showers, bbq etc etc. Fantastic set up if that is what you want.
I think that the advise would be, keep it simple, very simple otherwise you will run into all sorts of issues with carrying kit, who does what etc etc. Book a good secure area with toilets and showers if possible, offer tickets if needed but leave folk to make their own way. If someone turns up in a bus with loads of kit then lets have a party but otherwise keep it simple
This year one of the major issues was that P&O would not release car space tickets to the travel companies, this was because they could sell direct and keep the margin.
The Lotus Se7en club have had a few problems selling the package although most tickets have now been sold. It will be interesting to see what happens next year.