The Variants panel, located in the property column of the App, displays all information related to product variants.
In this panel, you can view, edit and modify prices: double click the cell to modify, enter to validate, that's done.
To modify in bulk, meaning applying the same price value to multiple variants in just a couple of steps, right click on the modified price > copy
Select the other variants onto which you want to apply the same price, using the CTRL key of your keyboard or using the mass selection icon on the toolbar> paste
This copy/paste option is a very efficient tool to apply the same value onto a selection of variants in just a clicks.