Mods- this is not Rumours or News. May I suggest T & E?
There is no closed shop. BALPA membership is open to pilots to take up if they want. It is a small organisation with an expensive infrastructure to support, hence subs are high. If people want to join, they are welcome, if they do not find it worthwhile, there is no problem in resigning. I don't see why there is any complaint. And contrary to some of the assertions early in this thread, BALPA subs do attract partial tax relief- at least where I worked.