Slitherine

How does the market affect city production?

If I remember correctly it has a negative maintenance cost which means every turn it gives a small boost on resources to all 3 resource types. It ignore the production values so means you can get small amounts of ore from cities with no access to it. It can be useful if you are struggling with a specific resource and when upgraded starts to generate a bit of income.

It's also useful for the city/cities that are specialized in troop production, since there will usually be 1-2 building slots left free even after you built a small fort, barracks, and a bath (for population increase). This way you can get a small resource bonus without having to spend workers on it. This is really nice since you usually need most of the population to build your army, especially late in the game.

The downside is of course the fact that it's a long-term investment. It costs 200/200/200 in total to build a market and upgrade it, meaning you will only benefit from it late in the game (and sometimes not at all). The "gossip" bonus is nice, but also mainly beneficial late in the game.