I recently found something simple but yet annoying: when you setup a product's price for a group, you click to make appearing a price form. But you can't remove this price form for a given group, is to said once you've setup a price for a group, you can't remove these price brackets anymore. At worst you empty all fields and validate: the price for this group will be 0.
Add "Delete" toolbar button. Once clicked it will ask user confirmation and once confirmed it will delete all price brackets (pricings) for currently edited product and currently selected user group.
Hint on that "Delete" button could be "Delete Group Pricing", so admin will know what exactly will be deleted, once button is clicked.