There is no moral obligation, only the terms and conditions. That's your actual obligation.

There's only one person who made a mistake here - Anthropic. They purposefully make their terms and conditions bad, and then when people played by the contract they set forth, they lost money. It's calling a bluff.

Anthropic purposefully priced this far too aggressively to undercut their competitors. Companies with stupid amounts of investor capital do that all the time. They flew too close to the sun.

You can't create a contract, have all the power in the world to rig the contract in your favor, and then complain about said contract. Everyone was following the rules. The problem was the rules were stupid.

To be more specific - abuse requires an exercise of power. End-users have no power at all. They have literally zero leverage over the contract and they have no power to negotiate. They can't abuse anything, they're too weak.