Oh, and the Variety magazine article states that Britney: Piece of Me has grossed over $20M dollars. According to the latest box scores, it did $18.3M from 27 shows. As of the publishing of that article, Britney had done 7 more shows (not including yesterday's). So, if it's over $20M, we can estimate it's around $23M give or take, which would mean an increase of 4.7M from the last box scores with 7 shows - 4,700,000/7 = average gross of 670K per show, which is close to the # Pollstar gave in its Mid-Year report.
However, I'd say it's a little less than that since each show wasn't sold out. So perhaps around a $600K gross per show.