Here is how preventing a merger led to lower prices and better products:

Stopping mergers is good for business. Take a very simple consumer product – razors and razor blades for shaving, or disposable wet shave safety razors.

Short version:  A couple of competitors to the disposable razor duoopoly went from online to store shelves, and forced the incumbents to reign in their high prices, particularly when one of the attempts to buy out one of the companies was stopped by the FTC.

It’s a 5-10 minute read, and well worth it.