Saruman's economic infrastructure unexplained?

[Maerbenn]

Originally Posted by Hot, crispy nice hobbit

Saruman was said to have started fortifying Isengard in 2953... which gave him 64 years to give birth to 10,000 Uruk-hai

From note 7 (an Author’s note) to ‘The Palantíri’ in Unfinished Tales:

The [White] Council seems to have been unaware, since for many years Isengard had been closely guarded, of what went on within its Ring. The use, and possibly special breeding, of Orcs was kept secret, and cannot have begun much before 2990 at earliest. The Orc-troops seem never to have been used beyond the territory of Isengard before the attack on Rohan. Had the Council known of this they would, of course, at once have realized that Saruman had become evil.