Our Cadets pay very little to fly. £90 pa for membership, and £8 for a winch launch and up to 30 minutes flying - a winch launch alone would cost me £8.50. It's true we don't offer all the other activities, but our cadets seem very happy spending a day on the airfield. They get very good at making sure they don't go beyond 30 minutes as it then starts costing 46p / minute, though the counting stops at somewhere a bit over 2 hours. I enjoyed flying 'for free' when I did my Silver duration, plus a few other enjoyable flights.
Like nearly all gliding clubs (and I suspect the ATC sites) public transport to the site is very poor, and that on it's own limits who can participate.