# if this city is built and the wall is completed
"if they build the city and complete the wall"
# any tribute, taxes, or tolls
"any kind of taxes.". This probably refers specifically to taxes on goods that people bought or consumed.
# tolls
taxes that people needed to pay to use roads
# and that will harm the treasury of the kings
They will "harm the treasury" by not giving money to the kings. Possible meanings for "kings" ... refer to Artaxerxes and his descendants or to honor Artaxerxes by referring to him in third person plural.