They get charged for outbound, not inbound (Score 1)

It only matters whether the greater of the two directions is reduced, if you do 8gig out and 1gig in you get charged for 8gig out, even if you reduce 1g inbound to .925G. (also it's 95th percentile typically, but that shouldn't matter in this case)

It would cost more to do the refactoring than the ever could hope to recoup, even if shorter urls also decrease outbound traffic.