A List of Revenues of the Darius I, Great King of Persia, is reported by Greek Historian Herodotus c 480 BC. This serves to show the greatness of Darius and the Persian empire, show who was paying tribute to the empire and how much they were capable of paying.
A talent of silver was a considerable sum of money, but making exact conversions to modern currency is problematical at best. Further compounding the problem are differences in how weights were measured.