A good candidate could have asked the questions you raised during the interview process. Why didn't you asked them before? In my experience, salaries of workers are based in their country of origin and or nationality.

Secondly, they will offer you base in your answers during the interview. A company will not offer you the stars if you were not impressive enough. Or, even if you were a hot candidate, they will not offer you the highest, you have to negotiate for what you think you deserve.

Good Luck