I get lucky when I get my inks I live about 20min away from CanogaCamera and the epson r1800 inks sell for around $12.00 compared to officedepot which is around $15.00. But I not have to change them that often, for some reason the r1800 does not drink ink like crazy. I was able to print a ton of 13x19 prints along with a good amount a 4x6 and 5x7 prints before my inks needed changing. Also the clogging issues with the epson inks are very minimal. I think i didn't print for like three months and it never clogged, I did a head cleaning and nozzle check before I printed and it was fine.
Also the mess factor with the epson inks is ZERO as where the CIS systems run the rick of a leaky line or fail connection, once that happens forget it pigment ink is very very hard to clean!