How Did Rockefeller Buy Crude at the Bottom?

David Senra says Rockefeller bought crude in large lots as the price was bottoming out, and he treated that timing as a central part of how the refinery made money.

The cost of crude swung wildly. He hired John Andrews, sent him to Oil City, and gave him one job: oversee purchases of crude. Andrews was to buy as the price was bottoming out and to buy in large lots, with little discretion of his own. His work was to keep Rockefeller posted whenever the crude market changed. Most of Rockefeller's early borrowing went to those purchases. When the price dropped, the buys were large enough to make the people around him nervous. Senra reads Rockefeller's words from the book: do not lose your nerve when the market gets to the bottom, because not buying then is a great mistake.

The edge on raw materials was timing and size, not a hope that crude would stay cheap.