OK - some figures I did in January based on Australian retail costs to operate an Epson Stylus Pro 9880:
Taking into account:
Autocutter Space Blades
Depreciation of unit over 3 years
Media (I did figures on Traditional Photo (Exhibition Fibre), Satin Canvas, Premium Luster and Textured Fine Art)
Including taxes, at full retail price, it worked out to about AUD$15.84 / sqm, plus 10% "wastage" gives $17.42 / sqm
Taking the Canvas cost - the total worked out at around $66.50 / sqm not including spraying or laminating or stretching or edging etc), which makes the ink about 26% of the actual cost, not allowing for labour.
For Premium Luster, the cost worked out around $41.50 / sqm which pushed the percentage of ink cost up to 38% of the cost.
Traditional Photo was in the middle at around $51.50 / sqm and Textured Fine Art was much higher at $73.50 / sqm.
So let's say on average that's about 30% of total costs are ink. This doesn't take into account wasted media, either, which would push the percentage down.
So, now consider what you would charge per sqm (1 sqm = 10.76 sqf). How much does the ink really represent out of your margin?
Of course every business wants to reduce costs and there's nothing wrong with that, but it's just a cost of doing business and for the return most professionals get it's not a big deal. If you also add in the cost of rent or real estate, insurance, perhaps staff, advertising, capital expenditure on equipment for framing, matting and such, it all becomes even less of a cost.