The cost of Epson ink for XP640 replacing all 5 cartridges exceeds 50% of the original cost of the printer. As soon as it was unboxed, set up and registered with Epson I noticed a "required" firmware update. If you install the updates, Epson is nice enough to hide enough software to prevent the use of any third party re-manufactured/refilled ink cartridges, chipped or not. As soon as suppliers figure out a work around, a "New Security Firmware" notification pops up. I simply refuse to be put in a position of buying proprietary Epson Ink. Highway robbery.
Avoiding the firmware seems to solve the problem for now. I bought the printer and as far as i'm concerned, that purchase was for 1 printer. I didn't agree to buy Epson ink, it's a rip off.