mining cost equilibrium is the bottom line value
its its cheaper to mine then buy people mine if its cheaper to buy than mine people buy.
so look for the most effiecient mining cost and you learn the bottom line mining cost which miners wont sell below
you soon learn the number of times the price went below bottomline mining costs ovr many years is negligable because people are not fooilish
But when one buys Bitcoin, one is not buying a specific amount of kwh of energy. If instead of Bitcoin, an egg would be a reward for generating a new block, your argument would sound like this: "mining cost equilibrium is the bottom line value of the egg". And this is obviously foolish.