Trouble for ULA is that they are used to cost-plus contracts. E.g. "I'll pay you 120% what it costs you to make." The incentive to maximize profits here is to maximize costs up to 80% of the highest amount the customer is willing to pay. For example, use obscure materials and manufacturing methods and lots of people in the assembly line. Better still if the rocket is built in parts in lots of different states and shipped around in pieces. Now with competition they have to go back and cut all those costs, which is not going to be easy.

(I used to work for Lockheed, although not in the missiles and space business. I wouldn't hold my breath expecting ULA to match SpaceX's prices.)