M2 cost of internal and external plastering/ intonaco

Thanks penny - that 'laborincasa' guide was really useful. It's good to see there is an average guide price for a final 'fine' coat of plaster of €9 something...our overall price for three layers of plaster on 40 year old tuffo walls (a 40 year old outbuilding so pretty regular) was €28. So  now we need to work out what is fair to deduct from the three layers plaster quote . It has already been suggested we can't just take off the going cost of a final layer of plastering but this just doesn't seem fair as although the builder did sand (by hand) and seal the walls with fissativo this was included in under 'decorating' in the preventivo but we still seem to be charged the full whack for the plastering....Personally i think we should just remove around €9 m2 off the €28 price. Does that seem fair to you?