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 as well as synergy effects between the different goods.
For Example: You sell a lot of iron -> the iron price drops -> another price goes up.
In addition to that there are random market events that also have an impact to the price calculation. The current prices of legal goods can be checked via the Market-App for the smartphone or via the User-Panel. Prices of illegal goods can only be seen if the Black-Market-App is installed.