It is outrageous that the printer manufacturers are doing this to us! From Slate:
To find out, I did what I normally do when I'm trying to save $60: I Googled. Eventually I came upon a note on FixYourOwnPrinter.com posted by a fellow calling himself OppressedPrinterUser. This guy had also suspected that his Brother was lying to him, and he'd discovered a way to force it to fess up. Brother's toner cartridges have a sensor built into them; OppressedPrinterUser found that covering the sensor with a small piece of dark electrical tape tricked the printer into thinking he'd installed a new cartridge. I followed his instructions, and my printer began to work. At least eight months have passed. I've printed hundreds of pages since, and the text still hasn't begun to fade. On FixYourOwnPrinter.com, many Brother owners have written in to thank OppressedPrinterUser for his hack. One guy says that after covering the sensor, he printed 1,800 more pages before his toner finally ran out.