Why was Parthia wealthy despite its decentralized political structure?

The Parthian Empire’s wealth was primarily derived from its strategic control of major trade routes connecting Asia with the Greco-Roman world. By dominating these commercial corridors, the empire facilitated the movement of goods and ideas, which brought significant prosperity to the region.12

While the empire maintained a decentralized, feudal political structure—governed by a small aristocracy that utilized existing Seleucid social organizations and tolerated various vassal kingdoms—this did not hinder its economic success. Instead, the Parthians leveraged their position as intermediaries in international trade to amass the resources necessary for extensive building activities and the accumulation of royal treasures, such as those found at Nisa.12