You assume you will have time to work on it. We are a business of 35 employees, 300k SAAS customers in low cost B2C, we are busy building product and fixing bugs there, we basically have zero minutes to spend on extending the billing system or implementing custom deals. Rolling out a price change can take anywhere from 3 days to 2 months (dealing with early efforts on custom deals is a nightmare). If it cant easily be automated, we can't do it. It takes too much time. If we had based our billing on a product like those mentioned here, we likely could have had way better chance of doing custom deals and rolling out price changes per customer segments.