Another thing I just thought of, in terms of maritime trade-vs-passive bonuses for coastal cities: The maritime superpowers have mostly only had a small number of coastal super-cities. Here in the US, they've changed over time. Boston, Charleston, Baltimore, and New Orleans aren't nearly the trade hubs they used to be. In the 21st Century, we basically have 3 coastal megaports: NY-NJ, Houston, and LA. Mind-boggling amounts of trade come through those 3 ports. The maritime wealth generated by every other US city combined doesn't match the trade going through even one of those 3 big ports. Even the wealthy US cities that happen to be on the coasts - besides those 3 - get their wealth in other ways. If you added up the wealth generated by the "ocean tiles" near Boston, Seattle, San Francisco and Miami today, it's probably a pittance.