I know some great offshore developers, and I also know some American developers that aren't worth their salt. Each assessment needs to be made at a personal level; you can't make a valid blanket stereotyped claim that fits everyone.
I'm in finance, not development. But my experience is that you get what you pay for. Good finance people in India are only slightly cheaper than here in the US; add in the off-shoring complications, it's a losing prospect. We save money on drone jobs, but that's about it.