Facebook advertising can help pay for itself, according to a case study the company conducted.

The report on Virginia Gov. Terry  McAuliffe's 2013 campaign, released Wednesday, noted the Democrat used the social media site's advertising to reach 494,000 voters. While that helped persuade voters and drive turnout, it also helped raise the money to pay for the ad buy.

That's because 58 percent of Facebook's "lead-acquisition" cost was offset by directing new email subscribers the campaign made through the social media site to a contribution form, according to the report released by Facebook and Bully Pulpit Interactive, which consulted for McAuliffe.

Digital consultants would argue that kind of return on investment isn't something that traditional media can replicate.