Townhall

Townhall does not require upgrades

The price of workers can and will vary depending on the demand in your zone

A player can also see how much prosperity each building has given Lumbermill Mine Smithy

It also shows how much prosperity you are going to collect for purchases up to this point. This is important because you will not return the spent prosperity.

Convenient chart of price changes in your Zone. Also, note that the prices in other zones may be different and even significantly different.