Though CUPS has its own quota system, there are other accounting systems you can use with CUPS.
The most well-known and feature-rich free software package for print accounting and quotas is PyKota (http://www.pykota.com/). We will discuss this in detail in a moment.
A simple system based on reading out the hardware counter of network printers via SNMP is accsnmp
. More information is available on:
http://fritz.potsdam.edu/projects/cupsapps/
There are other accounting tools that can be used with CUPS, including PrintAnalyzer, printbill, and LogReport.
You can find more information about PrintAanlyzer at:
http://savannah.nongnu.org/projects/printanalyze/
The information about printbill can be found at:
http://ieee.uow.edu.au/~daniel/software/printbill/index.shtml