It really isn't cheaper. Netflix pays $1bil/yr to aws. The only advantage streaming providers have is that you're already paying for an internet connection. But TV over internet solutions have been a thing for a long time so even this doesn't really matter. At the end of the day it's just bits going through a plastic tube from one computer to another. If anything, the 1 to 1 on-demand aspect of streaming would make this the more expensive option.