To change your min and or max prices in RepricerExpress there are a few ways you can do this -
Using the My Inventory section.
So first click on My Inventory and then on channel overview or product detail. Then click on the product in your inventory list you will like to update. There will be a screen pop up and you can simply update the base min and or base max fields with your new min and max price and click update.
Clicking on the amount that is in the need min/max section on your dashboard (if there are new products imported into RepricerExpress)
Search for a product you would like to update by ASIN, SKU or Title (see here)