ok, on the same theme of buying a printer and trying to work out (eventually) the cost per page..

say a toner cartridges average lifespan is 25,000 pages,

and you need a black cartridge and three colour cartridges..

Do I work this out multiplying their lifespans together? Does this make sense?

25,000 pages each, four cartridges = 100,000 pages total?

Am I way off the mark here?