If you can sign a yearly bandwidth commit (not sure what the minimum bandwidth requirement is, but 1PB / year may be in the ballpark) - you will get prices that are extremely competitive (maybe like 90%+ off base list pricing?)
You said 90% off which i’ve seen personally and amount to roughly 1c (most of the list starts at like 8-10c in the US). The sibling says they somehow got 90% off that original 90% which seems silly and def not something i would count on
What would your hypothetical egress arbitrage look like? Keep in mind we are specifically talking about cloudfront bandwidth - so being able to route to an upstream without that upstream also paying for bandwidth likely is not possible.