Yes. Our standard hourly rate for Datadog Pro is $0.03 per host per hour. You can choose to pay for all of your monitored hosts hourly, or commit to a subset of hosts upfront on a monthly or annual plan and pay any additional hosts on an hourly basis, billed at the end of each month. This works out to be much less expensive for extra hosts that may come up for a short period, but a bit more than monthly/annual rates if you ran on an hourly rate all the time.
The metering samples how many hosts are reporting data once every hour, thus the minimum increment for an hourly server is one hour. If that number exceeds your monthly commit, we just charge overage for the excess hosts.