you don't just make money from music sales. Miley's social media power was record shattering all with sales to back it up. $78 million seems a little high but she did make bank in 2013.
it's literally in the first paragraph of the article with a link to the source:
Quote:
Despite a public shunning from her risque MTV Video Music Awards performance with Robin Thicke in August, scandalous stage antics have been credited with earning the pop starlet $76.5million in 2013, according to Parade’s annual salary survey, What People Earn.