PoW is an environmental disaster because of its terrible incentives. When the price is low the amount of energy spent isn't such a big deal because it will be limited by the expected reward (which is low), but the more the price raise the more miners will spend to get their rewards (which correlates directly with a higher energy footprints).
And next time you think a "grey goo" or "paperclip optimizer" scenario can never happen, think of this. A clear cut case of it, we're just lucky humans were still involved so we can choose to pull the plug.
It's not about the price but about what is being secured. If Bitcoin's market cap was $1Q and used as a global financial settlement layer then there is some threshold where "it's just the price we currently pay"
That is an unsettling perspective. Bitcoin like a humongous casino. Its only societal value is to vent speculative impulses. When the tulip mania happened in Netherlands, one could argue, it was caused by wealth inequality. The tulip bubble represented a way to fly up the ever lenghtening social ladder. Makes you wonder.