State that by going through this process, you will firmly know which company will best meet your needs and interests. The company representative will either accept or not accept your proposal. You need to set a date and keep that promise. If you are still unable to determine if you want that offer by that date, you need to be aware that the representative may decide to look at other candidates. If your proposal is not accepted, you will need to be prepared to make a decision of whether or not to accept the offer on the company's timetable.
All cities have different cost of living standards.
This website will calculate the relative purchasing power associated with each of your salary offers.