The Guardian:

The sky-high price of printer ink – measure for measure more expensive than vintage champagne – has been well documented. Less well-known is the fact that the amount of ink in the average cartridge has shrunk dramatically.

A decade ago, the best-selling HP cartridge had 42ml of ink and sold for about £20. Today, the standard printer cartridges made by HP may contain as little as 5ml of ink but sell for about £13.

Cut open a HP inkjet cartridge and you’ll find what is going on.

This is a European report but there’s no reason to believe it’s not the same for cartridges sold here in North America.