Product documentation
In standard Microsoft Dynamics 365 for Finance and Operations a retail price adjustment is only applied if the sales price in the price adjustment is lower than the sales price on the item (or if found lower than a sales price trade agreement).
In order to make it possible to use price adjustments without setting up sales price trade agreements or a high sales price on the released product, we have made an adjustment that in case of a sales price of 0, the applicable price adjustment is applied.
When Price and Margin Management has been installed the retail price engine will treat a sales price of 0 on the released product as no price instead of a lower price, there is no separate parameter to turn this feature on or off.