FarmVille's Formula for Land Expansion

Ever wonder how FarmVille calculates the cost of land expansion?

Well, with the latest 26x26 land expansion being rolled out and currently available as a limited release, lots of farmers are wondering how the 2 million coins price tag for 26x26 land expansion is validated . Please note, not all farmers have access to the 26x26 expansion at this point. More users will gain access over the next few days and eventually everyone will have the 26x26 available in their FarmVille Market.

A FarmVille Freak came up with the following equation that FarmVille seems to have used for past, current, and future land expansions. He shared his equation via the official FarmVille Forum.