you already answered your own question. two different ways, actually.
one, you asked how long. as long as it takes them to get the expensive stuff through their supply chain (with a long lag to maximize profits, think like an oil company).
two, you illustrate the example of the company that lost a bundle by buying high and selling low. they could have held onto it with the hope that it would go high again, but they'd lose that bet, or they could dump it at a loss. but, if people are willing to pay high prices, they could hold onto it, and sell at whatever prices people are willing to pay... like they are now.
Nymphomania is not a disease - its a goal! (Methadist on Rosemary Kennedy)