[UshCha]

My son is in the busness in a small way.  The biggest cost in printing is time.  Printers are getting cheaper, a good one is probably about £800 for one that lasts a commercial timescale.   Using a safe value of say 3000 hrs life for the printer that gives you 26p an hour so just the printer alone so a 2 hr tank costs £0.52 p just in capital cost. add another 10p at least in spares,then probably 5% for the odd failure and its £0.70p  Time is not small 5 min to load, unload, clean and package so add al least another £1.  By this point its up to £3.0 with real estate and material.   Other costs , overheads and profit and its closer to £4.0 a go.    Now if you own a printer and do the maintenance yourself, don't charge man hours and don't consider real estate, its in your house, and profit is not an issue it is cheap.