Madonna's MDNA may be the first album to both top the Billboard charts and be a massive commercial failure. The record debuted at No. 1 on the charts, prompting her longtime manager Guy Oseary to herald the singer's comeback as a great success. And though it was quite a triumphant return, it turned out to be a short-lived one buoyed by what some are calling a cheap trick. MDNA sales have fallen a record 88 percent week-over-week, from 379,000 copies to a mere 46,000, Forbes reports. So why the...