Load a sh*tload of media into your printer with brand new cartidges and then rip and print another sh*tload of various files (ranging from heavy to light ink saturation) and print it all until your cartridges run dry... then throw it all in the trash and figure out what it cost you per square foot to do so. Subtract the cost per square foot of the media you just threw away and you will have your answer, give or take. Don't forget to add in the time it takes to deal with and make the [supplied] files actually printable.
In Romania the producers calculate the material 1-2 Euro. The costs for printing with Original ink depends on the quality of the print and is somewhere between 2.8 - 4,5 Euro / square meter. If you use third party inks, in much cheaper. So the production costs are somewhere between 5-6.5 Euros. One 440ml cartridge is 110-115 Euros.
I don't know how much do you pay for the printing materials.
When you give the final price to the cusomer, you should consider that you have to pay a lot of things :energy, the stuff in your company, printer usage, your time...etc.
So...sell yourself wisely!!!!!
You should really reconsider some alternative inks.
I hope this is usefull to you.