This is the best system currently available, and there are huge
improvements under development for CUPS 1.2:
Page counting will go into the backends (these talk
directly to the printer and will increase the count in sync with the
actual printing process; thus, a jam at the fifth sheet will lead to a
stop in the counting).
Quotas will be handled more flexibly.
Probably there will be support for users to inquire
about their accounts in advance.
Probably there will be support for some other tools
around this topic.