How is it disconnected from the costs of providing the service? This could only be true if all connections were built to support the maximum possible bandwidth

How is it disconnected from the costs of providing the service? This could only be true if all connections were built to support the maximum possible bandwidth all costumers are theoretically capable of. Because otherwise, the price you're charged is a mix-calculation - it's the price that's required to deliver the promised number of bits during a given timeframe.