Listing is an expensive operation. I don't know the exact economics of it, but it's very plausible to me that serving 1000 LIST requests has a comparable resour

Listing is an expensive operation. I don't know the exact economics of it, but it's very plausible to me that serving 1000 LIST requests has a comparable resource cost to transferring a couple GB of data cross-region. (It should be noted that this definitely isn't a market dominance thing - every S3 competitor I'm familiar with also charges per-operation, and charges 10 times more for LIST than GET.)