Since the beginning of March customers are no longer capped at 5TB for SharePoint Online storage and they may consume up to 25TBs.
Default SharePoint Online storage for customers is available based on the following equation : 10GB + (500MB * no of users) and customers can buy extra storage up to 25TB – see Understanding Storage Allocations in SharePoint Online
The price of SharePoint Online Extra Storage is now $ 0.20 Per GB/month. Coming from $ 2.50 this represents a reduction of 92%. See the full blog post here.
Additional storage can only be purchased with other SharePoint Online plans or any Office 365 E Plan