Supply and demand. There is no shortage of Bangladesh workers who would vie for employment at a very low price. In Silicon Valley, there is a dearth of employees who would take anything close to that price.
And if google is willing to pay 8:1 for jobs in Silicon Valley, things like work quality, locality, and language must be worth quite a bit to them.
Neither governments, nor companies, sit around and try to figure out how much "Should" people be paid. The market forces tell *you* what the relative worth is.