Interesting piece on the Taj Mahal.
20,000 people for 20 years is 145 million man days. At current cost of labour of, say, Rs. 500/day this is 70 billion rupees. Seems very high. What were the revenue streams of the king?
What was the population of the area at that time? A workforce of 20,000 per day on a single project would require a population ten times this size to service it.