It's a bubble, a fool and his money parted, etc. An object that has a limited supply, that gains demand, ultimately increases in value. Look at another farce that we as a society buy into, diamonds.
Bitcoin has been called worthless, bubble, etc. since 2009. It has seen dips and swells, and large ones. The more people interested in it's value or that want to acquire Bitcoin the more it's value will rise. Around 1% of the population may own bitcoin and that's at the high side estimate. There is room for more money in the game, which for a limited supply item means higher prices in the long run.
Will it boom or bust, if you knew you'd be wealthy.
Metcalfe's Law is the closest relationship that has been found with Bitcoin and it's price models. Metcalfe's law basically says that the value of a network is proportional to the square of the number of users on the network.
http://markets.businessinsider.com/...metcalf-law-network-effect-2017-10-1007560818