Saruman's economic infrastructure unexplained?

[Hot, crispy nice hobbit]

This sounds interesting...

I had always assumed that Saruman just "leased" some of the lands from King Theoden via Grima; just like how Grima borrowed Theoden's sword (many other things that men missed).

To be exact, however, Saruman was said to have started fortifying Isengard in 2953... which gave him 64 years to give birth to 10,000 Uruk-hai, build foundaries and furnaces within the ring of Isengard, persuade the Dunlendings to join his cause, and tutor Grima in the ways of clever speech... All out of sight from stragglers.

Saruman must have had some deep underground laboratories underneath the Misty Mountains...