Hi @leefur,
Since odrive allows you to access all of your storage, including your 9-10 Google Apps accounts, you could more easily manage them within odrive. You may not want to use company storage for that, though.
The cheapest general-purpose storage right now is probably Office 365/OneDrive, at least for 5TB. See here: Best options for 2TB of cloud storage?
As @amazon9 stated above, if you have mostly pictures, then Amazon Drive might work for you. Google Photos also allows unlimited Photo and video upload for free. Unfortunately Google Photos doesn’t provide an API to integrate to yet.