The picture below was taken as we drove south on I-77 through Charlotte and shows a total of five lanes, however, the two on the left of the barrier are for paying customers. So 40% of the total capacity (and 50% in other places) are set aside for those willing to pay for the privilege of zipping along during times when us poor folk are creeping along.
I have to wonder how much money is being lost since the government lockdowns have people working from home and using the free lanes is not a burden. That said, we saw some cars using the toll lanes anyway and wondering why anyone would bother spending even a few dimes to use them. Speeding is our best guess.