Did I got ripped off by the General contractor

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I recently built an in law unit of 911 sq ft and spent around 312 per sq ft to build this. The soft cost is around 15%. I paid the contractor around 270 per sq ft. Recently I was talking to a Chinese colleague and he said that I paid too much for it because he says he has a Chinese contractor who can do it for 150 sq ft for builder grade construction. The in law unit I built Is builder grade as well.  Nothing special about this construction. Is it really possible to build for that low in the Bay Area?