If there is a curve "amount of money a company of a given size will pay", in certain applications, server load, bandwidth, and disk space utilization likely scales far below that trendline, whereas per-user tracks far closer. It also ensures there is effectively no upper bound on CLTV as a given customer scales out, even if net-usage only increases logarithmically/asymptotically.
To try and be even-handed and take a more generous interpretation as well, the former is also less likely to be cogently communicable to a customer, and may have painful UX when limits are hit.