Booked room left unused costs a little

Room a booking holds that none of your sandboxes uses now costs a quarter of the memory rate, $0.001875 per GiB-hour, with no CPU charge; sandboxes you run bill as usual. 300 sandboxes of 2 GiB booked for 2 hours cost at most $2.25 if none run, and nothing if you cancel at least an hour before the start. A booking's answer, the CLI and the console's Booked room card say the most it can cost. See What it costs.