Anthropic Subscriptions Return About 5x OpenAI's API Value for Agents

SemiAnalysis’s comparison makes Anthropic’s plans look like the better API-equivalent buy for agent workloads. The gap is roughly 5x per month, with Claude Opus 5.5 measured against GPT-6.1 Sol. The comparison prices the same usage through each API and sets that against the subscription. That is not a small gap. It changes which vendor an agent team should test first.

Agent loops are where the math bites. A loop plans, calls tools, reads results, and tries again, so tokens pile up in a way chat does not. Run that unattended, and the subscription becomes the main way to buy tokens. A 5x spread is the difference between a side project and a real line item. The bill grows by the turn.

I would not switch on the multiplier alone. API-equivalent value is an accounting construct: it assumes both models finish the same job in the same number of turns, and prices one pairing, Claude Opus 5.5 against GPT-6.1 Sol. A plan that is 5x cheaper is not 5x cheaper if the agent needs extra passes. Test it before trusting the invoice.

Skip it if the usage is a handful of prompts a day; a cheap chat plan does not need this spreadsheet. For unattended agents, replay last month’s real traffic against both subscriptions before trusting the multiplier. A month from now, one of those invoices will look like a small mistake. The multiplier can survive that test, or it can evaporate.