I've had the R1800 for a month or so, and have been pleasantly surprised with how long it takes to run out of ink. I put in new inks and printed around 50 12x12 borderless layouts with complete covereage, plus 150 pages on plain paper (text and photos), and changed only one cartridge during our last show. That's pretty darn amazing if you ask me. I can't give you figures on the other printers (1280 and 2200), but we have tested how much it cost to print one particular 12x12 layout over and over until all of the inks were out, and it cost about $1.65 per side on the 2200 and 10 cents more on the 1280 (since you can't change out the individual color cartridges). That is the price of the paper and the inks, assuming that you print on both sides of the paper (and buy everything at full retail, which you shouldn't do

Buy.com has the paper at just about 1/2 off right now ). Of course, that price is going to vary depending on what you print, but really, that doesn't seem all that bad to me. I have no idea what it costs to print a 12x12 on any other brands of printers. I do know that the Epsons (especially the 1800 and 2200, which have pigment ink) are more archival than most other printers...and even more archival than prints that you get from the photo lab.
I do have to put my 2 cents in on the 2200 - I would strongly consider holding out for the 1800 (just a few more weeks!) if you are interested in printing layouts - it will do a borderless 12x12 and the 2200 will not (unless you trimmed down 13x19 paper of course). The 1800 also does a beautiful glossy print - the 2200 can print on glossy, I just don't like the results. On the other hand, if you aren't interested in doing the borderless 12x12 and don't like glossy, then I'd go with the 2200 - you'll get better b&w prints out of that one.