Probably not actually. Transferring one kilobyte across a network link has such a low value that the billing costs of aggregating it cost more than the revenue.
So instead you take a probabilistic approach - charge the user for a megabyte of data transfer 0.1% of the time, and bill nothing 99.9% of the time.
Now the typical cost is the same, the users bill is probably accurate to the cent, but you have divided the number of billing records by 1000.