BlakJak:
Streaming 4K costs them more. Why shouldn't they charge more?
Streaming 4K doesn't necessary cost them any more seeing your ISP are likely hosting an Open Connect appliance: https://openconnect.netflix.com/en/
So, it is just mainly local traffic for an ISP. Doesn't cost Netflix any more. Their HD/4K plan segregation where only the top tier get it is frankly stupid for this very reason.
At-least now they may have to rethink their plans given people will consider downgrading...