You can transfer a Cluster to another account in Hatchbox and this is done in the Cluster sidebar options "Settings".

You can find this setting by clicking on "Servers" in the top level menu to see a list of your Clusters, then select the Cluster you would like to transfer.

On the next page you will see the Overview for your Cluster, click on the Settings option in the sidebar and you will see the following:

Select the "Transfer" option and enter the new recipients email address. They will receive an email with a link to accept the transfer and then they can choose the account they want to assign it to.