You can purchase funnel fill carts for the 9890 and run anything through it. But like the previous poster says, then you have to worry about two things, first quality control with color consistency over time, and second longevity. There are some of these third party color pigments that have been tested by Aardenburg Imaging, but a lot haven't. Some have ok quality control and some don't. Some are very good gamut and some are really bad. Look at the results for the Image Specialists pigments up there that everyone was using a few years ago, not good longevity, and they are a big company and made ink for a lot of companies in the past. But maybe there is more than one Image Speialist ink? Worth considering all that. A lot of the longevity issues show up in the magenta channel for some reason. It seems like it is harder to create a stable magenta than you would think.
It all depends on what you want though in the end. If paying 2/3 less for an ink that looks good for a lesser period of time but allows you to crank out massive quantities of work is what you need, then go for it.
john