A lot of publishers wonder about their pricing guidelines: what works best? It depends on genre and type. In 2020, Kelly Peterson did an analysis of publishers that have tried a pricing strategy for eBooks that has varied from 9.99 and below vs 30% off the print price.
Below, you'll see a powerpoint containing the results of that analysis. Altogether, there were about 2500 titles in dozens of BISACs, so the set of titles really helps show the difference in pricing - and the impact that you see when you set proper pricing for your books.
Keep in mind that this pricing is regular pricing, and that books can be placed on sale for limited periods without causing an issue. Discount pricing for limited periods drives units but not necessarily dollars.