From NYTimes.com: H.P. Tries to Keep the Ink Flowing
H.P.’s printing group has long been one of the company’s star performers. It accounts for nearly a quarter of overall revenue. Printer ink remains one of the most expensive liquids on the planet — more valuable than expensive perfumes — providing H.P. with far higher profit margins than PCs and other types of computing hardware provide.
You know printer cartridges are expensive, but this is an interesting way to think about how costly the ink is.