Is there any way - whether OOB, JS, plugin, etc - to display the subtotal or sum of the number of records in each grouping in an editable grid?

A set of users desperately wants this feature so they don't have to rely on exporting to Excel or using the (horrible) reporting tool to quickly see how many records are in each group when "Grouped By".

The ONLY solution I've been able to find was a very pricey add-on from AppSource. Any help or guidance would be greatly appreciated!