Printer Costs

I am trying to bring home to users how much it costs to print an A3 sheet with about 90% coverage using an Epson Stylus Colour printer. All the costings I can find quote 5% coverage and whilst I can work out the costings from the amount of pages expected per cartridge and the cost of the cartridges, where can I find a sample of what 5% coverage looks like.

Can anyone help?