Texan frackers respond to price signals and the profit motive, not government quotas.

not 可以直接用在名词（或代词）之前，否定这个名词。

This is a story book, not a dictionary.

I like sports, not music.

本句，government quotas 跟前文的 price signals and the profit motive 是并列关系。not 的用法类似 rather than（而不是）。关键问题是，搞清楚 government quotas 跟哪个词语并列。