Calling current AI subscription services (especially Claude) "flat rate" (implying infinite access for a flat fee) is misleading. There are pretty strict hourly, daily, weekly, and monthly limits. So there is a pretty easy-to-reach limit for all these subscriptions. They're hardly unlimited, and given how easy it is to run into limits, it's likely not super complicated/low-stddev for an accounting department to figure out avg cost per customer.