It's very easy to calculate the actual cost given they list the exact tokens used. If I take the AWS Bedrock pricing for Opus 4.6 1M context (because Anthropics APIs are subsidized and sold at a loss), here's what each costs:

Cache reads cost $0.31

Cache writes cost $105

Input tokens cost $0.04

Output tokens cost $28.75

The total spent in the session is $134.10, while the Pro Max 5x subscription is $100.

Even taking the Anthropics API pricing, we arrive at $80.58. Below the subscription price, but not by much.

It's just the end of the free tokens, nothing to see here. It's easy to feel like you're doing "moderate" or even "light" usage because you use so little input tokens, but those "agentic workflows" are simply not viable financially.