Interesting read and points of view, I'm not a member but will come at this from a different perspective, that of someone with other interests but who cannot support everyone. So a few observations and questions.
Let's take BASC, 150,000 members at £82 a time (there are concessions to that, I'm an OAP so slightly less). How would AT fare if it increased the membership fee by £50 pa, would members leave in droves - I guess probably yes? So why do shooters pay so much more to protect their sport, because they realise it is under threat and attack from many sources and they need a strong political lobby, they are prepared to pay for this. They also have the Countryside Alliance and Game and Wildlife Trust (on scientific research) fighting their cause.
Angling is not there yet, they just muddle on thinking nothing will happen and maybe it won't? Anglers are not being attacked in the media on a daily basis with celebrities dangling dead swans caught in fishing line demanding bans and heaven knows what restrictions - this concentrates the mind more than percieved environmental issues that 95% of anglers neither see nor understand. If the fishing is rubbish in the rivers, go to a commercial for a day.
So I fork out my BASC membership each year, I hardly ever shoot now but that is how strongly I feel about it, wife sends some money to Countryside Alliance (which also have a fishery section) and she is a big supporter of moth and butterfly conservation as heavily into moth recording and about to start some butterfly recording for the local RSPB. I had many years of ACA, S&TA membership but pockets are only so deep and there are plenty of anglers to take up the slack.
Only when angling faces direct threats to the sport from the public do I think anglers will come together and pay up. We have to remember that angling is first and foremost a field sport so slightly different from other conservation bodies such as the butterflies, birds, badgers, mammals which all involve sitting and watching rather than catching or killing.