I'm pretty sure in this case it's anthropic doing the subsidizing because the api and extra usage rates are extremely expensive compared to the usage you get for the lowest subscription level. I pay $28 CAD per month and I'm pretty sure I'd burn through that in a day or two, and I'm not really a power user, I'm just using it to write code like it says on the tin. I seriously doubt there's a large portion of subscribers with low enough monthly usage that they'd save money by switching to the API.