RE: What am I paying for in WebResourceBase?
Hello!
WebResourceBase, altogether with RibbonClientMetadata are used to render the apps on browsers. The issue with these tables is that it will contain data from regular applications (Sales team Member, Service Hub, Sales Hub) as well as from your custom apps (either Canvas or modelDriven). They will also include images/translation files (resx files)/Scripts. It will also contain references to the files included on your solutions.
One common issue is that files that are added in a solution (let's say v1.0) might not be in use and on another iteration (v1.1) and as a result, those files are not included anymore. As a consequence, the WebResource file is left Orphan within your environment, occupying some storage.
Finally, another common issue is related to the number of records on the table. According to the documentation on https://docs.microsoft.com/en-us/power-platform/admin/capacity-storage#do-indexes-affect-database-storage-usage, records on table will require indexes. Some of the indexes are controlled directly by admins (Including fields into queries, or querying the table). Other indexes are generated automatically based on the usage, in order to improve performance.
Best advice would be to open a request with Microsoft Support to understand which of these (if any) is affecting the size on your environment and check if there's any possible action.