Don't forget that there are also grades of ink. The price of color ink cartridges that are specifically intended for high-end photo printing cost MUCH more than the generic stuff. However, as you noted, in this case the cost factor probably has to do with the non-ink features of the cartridge.
All of this is thoroughly discussed on web sites devoted to cameras and photo printing. That is, unless you are having a software problem, or a problem with the computer-printer interface, the use of color with Ubuntu/Gimp is much the same as it is for Mac/Photoshop or anything else. The *.icc and *.icm files are the same. The meaning of "gamut" and "perceptual" is the same. The only difference AFAIK is that Photoshop and other commercial software can do pre-press color separations in a format acceptable to commercial presses, whereas it's a challenge to do it with Gimp. But you don't need that.
So, to learn more about color, your best bet is to find your way to a site about cameras and printing. Before you do that, learn what the HSV and L*ab color modes do. Wikipedia has a good article on the subject. If you get into serious color adjustments, you may find that it's easier to edit in HSV or L*ab mode than in RGB.