people write "for free" (mostly in advertising copy). It's wrong. In the context of pricing or cost, "free", like "cheap", is an adjective. You would not say "You can get things here for cheap" and you should not say "You can get things here for free". "For" is a preposition and can only be followed by certain words or phrases. (e.g. This is for you. This blade is used for cutting some of our toughest materials). Like "slow" and "slim", "free" can either be an adjective (Get your free sample here) or a verb (I will free the bird from its cage), but it is not a word - such as a noun or a pronoun - that can be preceded by a preposition.