https://ir.netflix.com/secfiling.cfm?filingID=1628280-17-496...
says their 3rd party cloud computing costs increased by $23M in 2015 and increased a further $27M in 2016. More importantly, their total technology and development cost increased from $650M in 2015 to $850M in 2016. That includes engineers so it's a bit tricky to figure out what their costs really are, but they didn't go down appreciably in 2016 so this effect had to be in 2017. Looking at their first three 10Q's shows their Technology and Development budget keeps going up. I don't see how a streaming service could save 64% of its total computing needs, and it not show up on any of its SEC filings.
In 2016 they completed a seven year move of all their computing infrastructure to AWS. When they sized the system, they bought reserved instances (probably at a significant discount). From the math in this article, they bought 64% more than they needed if they just discovered they could save 64% of their EC2 budget. That seems like a big math error.