The property of an Authority is declared to be public property used for essential public and governmental purposes and such property and an Authority shall be exempt from all taxes and special assessments, except school taxes, of the city, the county, the Commonwealth, or any political subdivision thereof: Provided, however, That, in lieu of such taxes or special assessments, an Authority may agree to make payments to the city or the county, or any such political subdivision, for improvements, services, and facilities by such city, county or political subdivision for the benefit of a housing project or the persons residing on or occupying such premises, but in no event shall such payments exceed the estimated cost to such city, county or political subdivision of the improvements, services or facilities to be so furnished.