As you can probably tell from the image, I put up this question because ink catridges cost much but do not last long. Even extra large catridges seem to run out in no time, and the prices are still loftier than ever. HP (and other printer companies) practise tie-in sales by ensuring that only their type of catridge can be used in their device, so if you have an HP printer, you have a highly inelastic demand for their catridges. This expands their market power from printers to the ink catridges. It is anti-competitive and results in ink catridges of lower quality and higher price.