[讨论] PP Reading 2-4 13

Their choice was based on economic reasons – when the price of wood soared, as it occasionally did, they questioned the financial advantages of timber and predicted that it would be even more expensive as American forests became depleted.

The word "it" in the passage referes to ?

我选了 price, 答案是 timber .

有点糊涂,从逻辑上讲,到底是价格越来越贵,还是木材越来越贵?