Here is a basic price guide to resources:
The first few days on a brand new server most resources will be cheap as no one has money to buy them. After a few days resources like lumber and stone will be very expensive as they are used in building structures. These resources may cost more than 1 gold per item. Within a week or two of the beginning of the server prices will begin to drop as more players increase their own production of resources, capture valleys for bonuses, start raiding barbarian towns etc.
A few weeks later as the server gets more advanced prices of lumber and iron will go back up. They will get to be around 2 gold per unit. Food will even go back up around 1 gold per unit. Stone will not go back up though because the supply of stone will outpace demand. Once people raise their walls to level 9 and 10 they won’t need as much stone.
I’m going to try and track the prices of resources and put a chart in the advanced guide.