Most "enterprise" companies are paying full API costs. The subscription deals are only available to consumers. If you want enterprise levels of control over how your staff are using the models you need to pay up.

Not even close. "enterprise" companies are negotiating contracts. Call it pre-provisioned capacity, wholesale pricing, etc. Same is true for AWS, Azure, Salesforce, or literally any SaaS provider ever. There is a reason literally every single pricing page for any SaaS provider has an "Enterprise? call us" column.