How much did Harlech Castle cost to build?
The record: £8,190, 1282–89.
About $24 million in today's gold
3,900 years of a farm labourer's pay.
Caernarfon with its walls ran to £20,000+. Source
Who could buy it
The lowest paid on each ladder of 1350 whose pay was enough:
On a month's pay
In other words, out of a farm labourer's reach: more than a whole year of his pay.