Ciro Santilli
OurBigBook.comThe first human-made nuclear chain reaction.
Getting funding for the Chicago Pile Edward Teller interview by Web of Stories (1996)
Source. - youtu.be/mnScq24BEmc?t=114 the main cost for the reactor was the graphite. Presumably they already had the uranium in hand?. Edit, no, it is because it was a specialized graphite: Video 8. "German graphite from The Genius Behind the Bomb (1992)", i.e. nuclear graphite.
German graphite from The Genius Behind the Bomb (1992)
Source. Graphite was expensive because it had to be boron-free, since boron absorbs neutrons. But a boron process was the main way to make graphite. This type of pure graphite is known as nuclear graphite.