Yes but that isn’t changed by the amount of data used. There is no cost to supply per kb supplied, only a cost to maintain the equipment that governs the speed of the connection.

Here’s an analog example. If the city you lived in started charging you more for the water to come into your house faster as well as charging you for the amount of water you use. Obviously you should pay for the amount of a finite resource you use but the speed at which you acquired that resource should be limited only by the physics of the water transportation system.

Data on the other hand, is not a finite resource. There is no limit to the amount of data one can acquire given endless time and energy. So the only way to bill for that becomes the speed at which you acquire the data. You pay for the data speed and that funds the infrastructure to supply that speed indefinitely. End of story. The only reason data caps exist is that they want to charge more money for you to use less bandwidth so they can sell that bandwidth to other people. When what should really happen is, they should invest in higher bandwidth capacity and sell that to their customers to return on that investment.

Either supply me infinite speed and bill me for the amount of data used or supply me infinite data and bill me for the bandwidth. Not both.