The Internet is a mass of millions of privately operated connected networks. But at the core, there are the large providers and large consumers (of bandwidth). Netflix would have large connections to several of the largest Internet providers and those connections would each have their own commercial agreements. It might be that Netflix pays for access, or that the cost are shared, or that the third party is paying Netflix. These agreements would be negotiated on a per-ISP basis. Then the traffic flows from those larger ISPs to the smaller ISPs through similar peering/transport arrangements. As the relationships between the organizations become more asymmetrical, the financial pictures changes too. And eventually you have a smaller ISP paying to get peering/transport from a larger ISP and that pipe happens to carry Netflix traffic, when requested and routed.
Netflix is massive, it's one of the largest sources of traffic on the Internet. Netflix has many, many large connections between itself and the ISPs.
Further, Netflix uses a Content Delivery Network to ensure that content is "close" to users. If you watch Pulp Fiction tonight then when your neighbour (same ISP) watches it in the morning it's already cached relatively locally, it's not going to come back from Netflix source servers.
So Netflix and the ISPs actively work to minimize the traffic consumed.
Lastly, all data links have finite bandwidth. There's always costs for equipment and always costs for operations. Economically and mathematically there is not infinite capacity. These links can be astonishingly large, but not at all infinite. They're limited by physics and technology.
