The "bubble" is being driven by blockbuster earnings. The market is irrational but it's not brain dead.
Companies are paying Anthropic for more than just the model. Most of them would probably have no idea what to do with Claude without the harness, and Claude has the advantage of being specifically trained against that harness, whereas even the best open models have to figure things out for themselves.
Aside from which, many corporations can be relied on to chase that which is "industry standard" and/or "state of the art" rather than switch to an "open" (= no customer support) alternative that's merely "good enough" according to a rational analysis based in what they were doing a year ago. Even if it costs them far more. (We can see this from the fact that "tokenmaxxing" was a thing for a while.)