But if Comcast gets its users in the habit of using less bandwidth/data, won't that mean Comcast can delay speeding up their connection and providing more bandwidth? I think from that perspective, there is a long-term cost for them if their customers continue to demand better connections. So, you're right, there isn't a cost for each individual bit that's sent across their network, but instead there's an eventual cost for their users demanding a connection that requires an upgrade to their infrastructure. And that's a cost that could be delayed if they change the behaviors and/or expectations of their customers.

(and fwiw, i have no interest in defending comcast. i bring this up mainly inform myself about the circumstances.)