Bitcoin was made to pay for Pizza.
As Bitcoin gets more expensive, it starts to squeeze out more and more average people from using it to pay for what they need.
Bitcoin maximalists already have the bag so the dominant strategy is to get institutions and corporate with lots of money to come in to pump their bags, while leaving more and more people and use cases behind.
Sustainable? I guess the question is why wouldn’t the institutions cooperate instead and release big boys coin and leave the former plebs holding onto their bags without further upside?