Evony is free to play, but that doesn't mean optional perks in the game are free as well.

You can choose to pay for the additional features in the game, but you don't have to pay to get them (most can be earned through luck on the wheel or through the work of attacking other players/npcs), nor do you have to pay to create an account and start playing the game. Nor are these additional features essential to prosper in the game.