If you have an ASN in North America you can get settlement free peering with most networks. That means all you pay for is the hardware/power cost to transport your content. Usually this is fairly unbalanced, and providers will compensate eachother (reach a settlement) if data is too skewed in one direction, almost always in the datacenter's favor (as ISPs are really upstream light).

Comcast, Verizon and others have recently tried to turn this on its head by witholding peering upgrades to Netflix, who wasn't even charging them a dime for all this data that their customers requested! This is not net neutrality, and performance degradations like this made Comcast uncompetitive in my neck of the woods since I have Fiber available by rare happenstance. That being said, my fiber provider (Centurylink) has even worse peering with Comcast, such that loading xfinity.net is a chore on gigabit fiber, let alone the Xfinity Go app. These performance issues caused me to cancel my TV service with them and get a different provider that worked better on my kids tablets, and so long as providers play games to throttle eachother, stories like this will be common.