Do any hosts use the "Maximum Concurrent Users" cap in IIS (I'm guessing Apache has something similar) to explicitly limit the maximum number of concurrent connections for hosted sites?
Most hosts place limits on data transfer/disk space, but don't explicitly put a limit on maximum concurrent connections, or use this as a package feature e.g. most basic package = 20 connections, top package = 150 connections, etc.
I'd have thought this would be a nice way to avoid any dispute later by stating it up front as part of the package features, but it doesn't seem to be done anywhere.
Then the user could always upgrade to a higher package if need be, so their payment amount is consistent with the server resources used.
I'm aware that this measure is not the 'be all and end all' of measuring the extent of resources used, but would seem to be more useful than is given credit for; if a site on a basic package consistently has say 80 concurrent connections maxing out at over 200 (whether it's because their scripts are slow, their images large or just that they are very popular), then clearly it's time for that user to upgrade.