Same here with my FB6100 (V3 from HP), but I've had both Fuji and Nazdar approach me about switching to their 3rd party brands. The Fuji ink (Color+) is supposed to have a wider gamut and use less ink but I think it's pretty much the same price as the HP OEM. I have my rep looking into it. He said they'll come in, do the entire ink switchout and if I don't like it come back and reload the HP stuff.
I said if it doesn't cost me less per liter, then it's going to be a hard sell. Telling me one liter of Color+ goes further / lasts longer than a liter of V3 is marketing. Save me money on the front end (by the liter) and I won't have to wonder if I'm really getting better ink mileage.