They've given talks about how they do their own internal billing scheme to manage their blend of on-demand vs RIs vs spot. It comes down to watching your usage

They've given talks about how they do their own internal billing scheme to manage their blend of on-demand vs RIs vs spot. It comes down to watching your usage patterns, doing some smart modeling on growth, and buying RIs for the amount you'll utilize to the point that it makes sense over on-demand. RIs make such a big difference on your bill if you utilize them well, and it's a no-brainer for Netflix scale.