We use the 775ml cartridges with the 365 and not sure if it's 100% correct, but it's close enough. We are also very dependent on the online cost sheet (but it's shown AFTER the job is complete...hard to quote with that) So, we decided to figure ink cost based on square footage/milliliters. Gives us a little wiggle room but good way to estimate. We added up the cost of all 7 cartridges and divided by the total number of mL, so (152*7) / (775*7) = 1064/5425 = .196, so....19.6 cents per mL
With that number ($0.196) we can apply it to the quote for square footage on a bid. Example: 48" x 96" media (cost $.23 per square foot) (4*8)*.23 = $7.36 media PLUS 32*.196 = $6.27 ink TOTAL ACTUAL COST: $13.63
As I mentioned earlier, this gives a HIGHER than normal ink cost, but is a pretty good starting point IMO.