It's only free for a small amount of content or when you're ad supported. If you get significant traffic or care about performance, someone needs to pay for it.
No one pays for bits moving around on the internet, for the most part. See “peering internet.” Big companies just charge you for it to prevent it from being abused.
You might want to learn a bit more about how peering works. It's definitely not free even if the major players have reciprocal agreements — just ask Netflix how free that was when Comcast wanted to double-charge them.
