The dromons cost 600, the galleys 500, but the dromons have a lower maintenance than the galleys.
Having a decentralized system of government creates economic difficulties, but makes the game more interesting. At the same time, I do not think I have ever played a game with so many calamities happening in such a short period of time immediately after the start of the campaign - two famines and a flood in less than 15 years (approximately once per 5 years). The fact that the famines hit the two richest provinces and the flood detsroyed the improved farmlands in Genoa made things even worse.