Leonardo Da Vinci Castle

In case you should wonder where so much money could go in a week, we would have you know that we have needed – and shall continue to need 400 masons, both cutters and layers, together with 2,000 less skilled workmen, 100 carts, 60 wagons and 30 boats bringing stone and sea coal; 200 quarrymen; 30 smiths; and carpenters for putting in the joists and floor boards and other necessary jobs. All this takes no account of the garrison ... nor of purchases of material. Of which there will have to be a great quantity ... The men's pay has been and still is very much in arrears, and we are having the greatest difficulty in keeping them because they have simply nothing to live on.
One detailed study has been done on the cost of construction of Langeais tower, built in 992 in France. The stone tower is 16 metres (52 ft) high, 17.5 m wide, and 10 m long with walls averaging 1.5 m. The walls contain 1,200 cubic metres (42,000 cu ft) of stone and have a total surface (both inside and out) of 1,600 square metres (17,000 sq ft). The tower is estimated to have used 83,000 average working days to complete, most of which was unskilled labour.
Not only were stone castles expensive to build in the first place, but their maintenance was a constant drain. They contained a lot of timber, which was often unseasoned and as a result needed careful upkeep. For example, it is documented that in the late 12th century repairs at castles such as Exeter and Gloucester cost between £20 and £50 annually.
Medieval machines and inventions, such as the treadwheel crane, became indispensable during construction, and techniques of building wooden scaffolding were improved upon from Antiquity. Finding stone for shell keeps and castle walls was the first concern of medieval builders, and a prominent concern was to have quarries close at hand. There are examples of some castles where stone was quarried on site, such as Chinon, Château de Coucy and Château Gaillard.