What membership? Do you get a gold membership when you buy gold, or an euro membership when you buy €? Schemes need you to bring others to invest, with bitcoin you don't care if your neighbor gets in or not. It would benefit them, but its their problem if they want or not to buy, and bitcoin certainly doesn't care, it does NOT depend in the inflow of money from people buying it.

Bitcoin price is a simple free market result, it is useful enough to the group of people that own it, because they perceive it so, and that's what truly defines value. This can change at anytime and this is what fluctuation reflects. Over a decade, however, it has been gaining.