The Forbes piece lays out where these un-referenced, anonymous "U.S. financial experts" got it wrong, stating that although the gross profit from her tour ($4 million per individual show, $280 million estimated altogether) would put her on that mil a day number -- but, as Greenberg points out, "...Robert Downey, Jr. doesn’t earn $1.5 billion if the latest Iron Man movie grosses $1.5 billion, and the same holds true for Swift (and her peers) when it comes to touring." Remember, she still has to pay vendors, agents, background dancers, hair stylists, and myriad other members who put the spectacle together. The problem was then expounded by by second-hand sources recycling the initial info, without doing any serious fact checking. That number would mean she would probably make more than Jay-Z, Beyonce, and Drake, combined -- by a considerable margin.
So what does this all mean? To use another prominent internet idiom:
Tl;Dr -- T. Swizzle is god damn rich, but not that god damn rich.