Ink or Blood?
"Over the life of your printer, you'll probably pay more than 500% of the total price of the printer itself on ink refill cartridges. At $30, a 42ml cartridge of black printer ink comes out to 71 cents per ml. On the other hand, the Red Cross charges $200 for 500 ml of blood, which comes out to about 40 cents per ml." - Amy Bell, "6 Outrageously Overpriced Products", Investopedia