I know Office 365 Enterprise plans offer "unlimited" space:
- Unlimited OneDrive storage for E3 or E5 subscriptions of five or more users. Microsoft will provide an initial 5 TB of OneDrive storage per user. Customers who want additional OneDrive storage can request it as needed by contacting Microsoft support. Subscriptions for fewer than five users receive 1 TB OneDrive storage per user. F3 plans include 2GB OneDrive storage per user.
Definitely not $10 per month. I have one of those accounts, so far with 50TB, 25TB in OneDrive and one personal SharePoint page of 25TB. I tried some time ago to request another increase but got a lot of pushback from Microsoft, since I don't need it, I didn't push further, so my guess it's really a YMMV and a lot of paperwork/pain.
Finally, Microsoft has artificial use limits based on your average usage. So if you usually don't use it much, downloading all your data is a huge pain as you will get throttled pretty quickly. Happened to me once that I needed to recover a lot of data, rclone was throttled pretty bad, but I was able to use their official client and a windows middleman machine wrapping the encryption with rclone to bypass throttling.