Most of you probably don't trifle with little printers like the one I have at home, so my experience won't correspond too well to yours, but in case it might be of interest:
I kept detailed notes about the precise areas printed and the ink cartridges used, and I examined the ink remaining at the end, for my Epson R280 printer, for the year from May 31, 2017 through May 30, 2018. This is a six-color (CcMmYK) dye-ink photo inkjet printer. I printed 189 photos with a total area of a little over 74 ft^2, using a little over 146 ml of ink for all purposes, including self-cleaning and ink left in the cartridges when they were replaced, for a total use of 1.97 ml of ink per ft^2 of photo printed. Put another way, that’s an average of 1.09 ml of ink to print an 8×10 inch area.
I also tracked my actual costs of ink purchased during the year. The average (including delivery charges and sales tax) for all ink bought comes to $1.65 per ml. Therefore, my average cost of ink per 8×10 inch area printed was $1.80. This includes ink used in self-cleaning and left in changed-out cartridges.
With Epson Ultra Premium Luster and Premium Matte papers, in my use mix, my average paper cost was about $0.47 per letter-size (8.5×11 inch) sheet. Therefore, my consumables (ink and paper) cost averaged about $2.27 to print an 8×10 inch image on a sheet of letter-size paper. Of course, at the high end I also really liked Hahnemühle Photo Silk Baryta 310, which runs more like $1.16 per letter-size sheet, so $2.96 for an 8×10 inch print.
For whatever it tells you in part about the printer and in part about the images I printed, given that with 6 ink colors 17% of the total ink consumed would be average, my actual fraction of the ink used for each ink color was cyan 12%, light cyan 24%, magenta 12%, light magenta 25%, yellow 19%, and black 7%.
Methodological issues
● As soon as the printer driver indicated that a cartridge was empty, I changed it. I did not wait until the printer simply stopped printing, as some people do. This is probably overly conservative / protective of the print head. But I accounted for ink use and cost in the way I actually operated.
● My little R280 really did not use that much ink that didn’t go onto the paper. Over the whole year I only had to trigger one self-cleaning (after the printer sat without printing for 55 days). Some ink probably got wasted with each cartridge change. Also, I printed 10 nozzle checks, but those use very little ink. As much as I love the Canon Pro-100 we have at work, it uses a lot more ink on (unavoidable) self-cleanings.
● Ink use depends on whether you’re printing a color or a black and white image. I printed both, but much more color.
● Ink use depends on media settings, and very likely varies among glossy, luster, matte, etc. papers. I used a mix of papers: probably mostly luster and matte, but also, glossy, semi-gloss, and others.
● Although I estimated the ink remaining in the printer by counting the fractions of the ink shown on the driver’s monitor (which displays at 52-pixel precision), which appears to be more an estimate than an accurate measurement, I don’t think this is a significant source of error. Every cartridge was changed multiple times, except for black, where I used just over 1.5 cartridges. As a result, I’d be very surprised if my per-channel ink use estimates were off by more than 10%. Because errors are probably closer to randomly distrusted, I suspect that my total is within 5% of being correct.
● I used a mix of ‘standard’ 78 cartridges (reportedly containing 7 ml of ink each) and ‘extra-large’ 77 cartridges (reportedly containing 11 ml of ink each). Basically, I bought two complete sets of extra-large 77 color cartridges, but I also bought a bunch of standard 78 cartridges to ‘fill in the gaps’ because light magenta and light cyan, and to a lesser extent yellow, got used a lot more than the other colors. The 77 sets do not contain a black cartridge, and 77 black cartridges don’t seem to be readily available.
● Logically one should think that the more ‘light’ inks a printer has, the more ink it will use per area printed. Light inks are basically diluted regular inks, and in their absence the printer would mix smaller amounts of regular inks with more unprinted white space. Therefore, if all else were equal, then I would expect a four-color (CMYK) printer to use less ink per area printed—and, say, an eight-color (CcMmYKGg) printer to use more.