AWS appears to be the best product for the job in terms of cost-effective scalability for their needs. That it happens to be a profit center for a competitor is

AWS appears to be the best product for the job in terms of cost-effective scalability for their needs. That it happens to be a profit center for a competitor is a side concern. Furthermore, it's actually a benefit to the marketplace! It forces Netflix to differentiate it's product to retain customers/marketshare.