That's not how I read it or what their example says. As I understand it, if you create a bucket and then delete it again within the hour, you only pay for one hour. I think the 5€/month is if you have active buckets the whole month, since it's less than if you actually had to pay for all the hours.

30 * 24 * 0.0081 = 5.83

28 * 24 * 0.0081 = 5.44