10Gbps EC2 instances start at $0.742/hour. Welcome to the cloud. ;-)

I assume the cost is in retrieval though and counted per the Job Creation API, regardless of whether and how quickly you download the data.

but you're right that the 3TB/hour use-case is very hypothetical. Internet archival is just not suitable for those kind of volumes. I think the point OP was making that mistakes like using archives that are too large, or requesting many at once could cost you a lot.