A report can be run to show the impact of the Pricebook before it is run. This report can be accessed from the Product Pricebooks page or from within an open Pricebook.

From the Product Pricebooks page open the spill menu at the end of the line and choose Pricebook Product Price Comparison. Alternatively open the imported Pricebook, and from the More Options menu select Pricebook Product Price Comparison.

Select the Price level and any other filters before choosing Run Report. This brings up the Pricebook Product Price Comparison report, allowing you to see the current product price, the Pricebook price and the change.