The states and other government agencies pay for any roads necessary to get to the access ramps. When you get on a toll road and pay what ever the price is. Everyone else takes the toll roads. State networks and other government agencies are on their own. Most of the existing NSFnet traffic would go over these commercial networks which would have to be paid for by the users.
Super computers fill a diminishing niche in science and industry.
Applications of this nature are a bit obscure. These applications would demonstrate, and not necessarly do anything useful.