All prices for farming goods are dynamic and will be calculated globaly between the different servers. That means the price for iron bars on server 1 is the same as on server 2. The price calculation is a complex process and depends on the number of items sold and synergy effects between the items.
The current prices of legal goods can be checked via the Market-App for the smarphone or via the user-pannel. Prices of illegal goods can only be seen if the Black-Market-App is installed on your smartphone.