Given the cloud ecosystem (and associated markets), I would be noteworthily surprised if an average datacenter/colo's smart-hands facilities wouldn't be able to accept me mailing in some HDDs, having them attached (possibly by renting multiple additional servers and having them installed in there), then later disconnecting them and printing a supplied prepaid shipping label to return them.

(I'd provide an appropriately oversized tip to ensure a near-unreasonable amount of bubble wrap is included in the return.)