Of course it's not how many pages one can do but the cost of the cartridge, me! I use after market ones which are 2.99 each and have nearly three times the amount of ink in them 19ml against 7ml in the real Epson ones, rip off or what.
Aftermarket cartridges are fine until they bu99** up the printer. Working in the graphics industry for years I have seen countless printers trashed by poor quality cartridges. If it is lots of pages you need often, get a cheap laser printer.