It really does not matter how much they pay because the market price does not include the actual costs a company imposes on the environment. There is no CO2 Tax, is there?

Ask yourself: How can it be more efficient to stream the same stuff over and over again, wasting CPU cycles on couple of fat machines etc. instead of playing it from a local cache (hard drive, ...). IMHO it cannot be more efficient. It is convenient and it appears to be cheap.