do chef and puppet cost money?

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http://serverfault.com – I intend to use chef or puppet to do administration (i'm thinking more of chef as its younger and i get a better feeling about it). In both home pages i saw there is an "enterprise edition" that costs money. I don't intend to buy anything, what would i miss in chef / puppet if i don't buy them. what does chef offer that costs money exactly? what does puppet offer that costs money exactly? it was not so clear to me from their web site kind of obscure. (HowTos)