[adrianmonk]

Maybe some sampling mechanism comes along and takes a snapshot once per hour.

Suppose you store the data there for 6 minutes. Then there's an 90% probability that the sampler misses it entirely and you pay $0. But there's a 10% probability that the sampler does catch it. Then you pay for a whole hour even though you used a fraction of that.

Over many events, it averages out close to actual usage[1]. In 9 out of 10 cases, you pay 0X actual usage. In 1 out of 10 cases, you pay 10X actual usage. (But you can't complain because you did agree to 1-hour increments.)

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[1] Assuming no correlation between your timing and the sampler's timing. If you can evade the sampler by guessing when it runs and carefully timing your access, then you can save a few pennies at the risk of a ban.