Unless there's some kind option where youtube or twitch signs a contract with select creators and then hands them huge sums of cash upfront for the costs of future content production, or to license the creator's existing content to distribute via youtube/twitch then the cost of getting that content is still just as free for youtube/twitch as it is for the pirate streamers that upload bluray rips.
Ad revenue is money gained from advertisers at the expense of viewers, it's entirely separate from the cost of the content being viewed.
