> AI infrastructure is supply constrained

It's supply constrained in terms of global hardware production capacity, but that's not how it works for any given company. If Anthropic wanted more GPUs for customers paying them enough money to outbid the next guy in the market for the finite number of GPUs then they would do that and get a higher percentage of the finite number of GPUs.

So the cost of using more internally is still their own cost, i.e. the price of being the high bidder on more compute resources, not the retail price they charge to customers.