There is in fact a type of pricing called Standard (On-Demand): Pay-as-you-go for input and output tokens. But you can also have a provisioned (PTUs) pricing, which I'm guessing is what you have.

"Provisioned": You can allocate and manage throughput for deployments, ensuring predictable performance and stable capacity. You are charged an hourly rate per model regardless of usage, but you can also secure additional savings through monthly and annual reservations.

You can also read more here.