There's at least a couple of reasons that your analogy doesn't really work.
First a lot of these roads are 'free' and yet you're still being charged for it. If two large networks come to an agreement then they connect the two networks (ie build that road), but no money changes hands.
Second if there is a paid peering agreement in place (ie say AWS had a cost to push your data out), that still wouldn't be billed to them in the way they're charging you. Instead they'd be paying for the rate of traffic at something like the 95th percentile of the max. This means that you could download a petabyte of data from them when the pipe isn't busy and cost them nothing, or you could download a gigabyte when it's busy and push up the costs.
First a lot of these roads are 'free' and yet you're still being charged for it. If two large networks come to an agreement then they connect the two networks (ie build that road), but no money changes hands.
Second if there is a paid peering agreement in place (ie say AWS had a cost to push your data out), that still wouldn't be billed to them in the way they're charging you. Instead they'd be paying for the rate of traffic at something like the 95th percentile of the max. This means that you could download a petabyte of data from them when the pipe isn't busy and cost them nothing, or you could download a gigabyte when it's busy and push up the costs.