I do think it's rather expensive though, more than all the other forums I'm subscribed too put together!
Look at what you get for your money. How many of the other clubs you're in offer such heavily subsidised events. For example, where else are you going to get an open pitlane trackday, on a proper UK circuit, on a Saturday, for £50?
Another reason for the high (well, higher than it used to be) joining fee is to hopefully try and attract more genuine enthusiasts, and keep the chavvy, 5 minute fly-by owners away.
It's far from being the most expensive club as well. I'm a member of the MLR, and that's £35 per year.