For the most part the skills have been free, but not anymore because it looks like Amazon wants to monetize it. The company has recently announced that they will now be introducing paid subscriptions for “premium” Alexa skills. Right now it seems that one of the skills that will be taking advantage of this feature will be the Jeopardy! skill, where it will cost users $1.99 a month.
However the good news is that if you’re a Prime member, Amazon has stated that access to premium skills will be free. Presumably this is one of the ways that Amazon is trying to get customers to sign up for a Prime membership, which includes expedited/free shipping, exclusive deals, access to video/music streaming, and more.
In a statement provided by an Amazon spokesperson, “Bringing a subscription model to skills for Alexa will bring customers the benefit of new, engaging, and high-quality experiences while providing developers an additional way to earn money from their skills.”