This migth be somethign with the new UI but it didn't seem very intuitive and is a bit of a step back in my opinion.
When adding prices to a price list, especially after copying a sales price list to turn it into a cost price list, it's very useful to be able to step through each record one by one and correct the price. You used to be able to do this with arrows in the top right. You seem to have a panel you can expand from the left of the screen but it only shows you 4 items from the grid, you then have to navigate back to the price list and find your role prices, move to next page then start editing again. It's a very bad user experience.
You need to allow the user to continually scroll through all the items in the role price list without having to navigate back.