Oh! And Born This Way is a 10 million seller too.
Telephone (ft. Beyoncé) is around 9 million right?

According to this both sold 9M.

http://atrl.net/forums/showthread.php?t=175622

Add Britney to the singles:

BOMT = 10.5M
Scream and Shout = 10M

The thread is just outdated. They've all been certified for as much or more as the Katy ones that are being considered 10M plus.

"Telephone's" sales add up to less than 8M and it sold less than "Scream & Shout," an 8.5M seller, in every country sans Japan