Yes it is and it happens all the time because of salary negotiations. The same thing applies to location based salaries - nobody will want to work if the offere

Yes it is and it happens all the time because of salary negotiations. The same thing applies to location based salaries - nobody will want to work if the offered money is not adequate. If company X from poorer country Y wanted to open an office in SF they simply wouldn't be able to find anyone that is willing to work for the same amount of money that is offered for country Y employees.