As long as bitcoin has intrinsic value (which we agree it does), the price can boom due to economic conditions, just like the precious metals.
where's the intrinsic value? i don't believe anything has intrinsic value in the great scheme of things. value's awarded and mutually agreed, it's not a concrete thing.
you're right, all value is necessarily subjective because value is a human construct that doesn't have an object existence you can prove with experimental or observational evidence.
However, Landauer's principle of information theory ensures that entropy-increasing, irreversible computations (like bitcoin's proof-of-work hashing) consume a quantifiable minimum requirement of energy. Energy is an objective, extrinsic property associated with many different tradeable commodities that are widely marketed. i.e. valuable, across the planet.