Back to Basics was a real success. 4.5 million copies sold worldwide, 1.7 million of which were sold in the US despite its selling price of between $17-21 because it was a double album. And all of its officially released singles went platinum in the US during the start of the digital era. Wow.
Also the real deal here is how YB and JAF gave Christina back-to-back Gold singles in the US. With proper promo and push from RCA, both singles would not have a hard time selling a million copies and could have really saved the Lotus era.