Something like 15 euros a night springs to mind. I can't remember if that is for a single or a double though.
For the Panormitis festival on 7 November they also put out mattresses in the refectory every night and people sleep on the floor.
ops:
Spent 3 months on my own there on our yacht back in '93 and it was seriously quiet then. That was before the first call boxes and pay phones. The only link with the outside world was a wind up phone in a cubicle under the stairs. The road over the mountain to Yialos was a dirt track impassable to anything except off-road vehicles.