Have you tracked usage? What I am driving at is how many square feet do you get from the carts? I tried third party ink and was shocked at how fast I went through them.
Started tracking cartridge gram weights on identical files and found the savings not to be so great. This was most likely due to a much higher solvent load. There was a lot of "overspray" on all components under the covers also.
Granted this was a few years back and things my be better now.