Katy may have snatched Gaga's wig on the #1 singles front, but she can't outsell Gaga when it comes to album sales and concert tickets. I don't know how much Katy's TD tour grossed, but I'm sure it wasn't anywhere close to the 227 million TMB grossed. And if Gaga released a concert movie, I bet it would do better than "Part of Me":

Domestic Total as of Aug. 6, 2012: $24,832,407
Foreign: $4,897,888 16.5%
= Worldwide: $29,730,295

http://boxofficemojo.com/movies/?id=katyperry.htm

Maybe it's just me, but that's not a very impressive sum for someone who's supposedly so popular and snatching so many wigs. Katy's popularity is limited to the Hot 100, it seems.