It's also about leverage and options. I'm familiar with the software dev world and the circus world and am a professional in both - and I've been on circus contracts where I do practically the same exact job as someone from the Philippines (on the same exact show) and yet get paid 2-3x as much. It's price discrimination based solely on nationality and your alternative options, and I've seen it in person. In fact - I am a dual citizen, native to both cultures (moved at a very young age); if I applied for a contract using my U.S. passport and my foreign passport, I would get two very different offers in terms of compensation, for doing the exact same job.

The people spouting "it's all about how much value you produce" are so naïve and ignorant of their privileges / market realities that it hurts.

With devs the compensations will match only when the good foreign developers have just as many alternatives as the good U.S. developers (or at least close to parity - exact parity will never happen due to jobs that simply can't be offshored - contracts with government agencies, for example)