Some of the temples had small treasuries where the offerings were kept. There was one on the Acropolis itself as I recall and also I remember seeing one at the ruins in Delphi. The Acropolis overlooks this site. There is major excavation going on in the agora area now and some new buildings have been discovered in recent years. There is a small, very nicely preserved temple within view of the reconstructed agora colonade and I don't doubt others existed in the area. Clearly there was a lot of commerce and religious activity in this area, so money was probably banked there in one of the buildings.