Andy Mallon shows how to move your backups up to Azure Blob Storage:
Geographically-redundant storage, on a cool access tier currently costs about $0.02/GB. That’s a fraction of what it would cost you to have it on your NAS, let alone having multiple geographically redundant copies, and the effort to set up and maintain your copy to off-site.
And up to a certain size, it’s faster to retrieve the backups from Azure than calling the off-site storage company.