What is the best global banner mobile ads network for android apps? (except AdMob)

I usually use only AdMob banner ads and the PPC is about $0,03.
But, there is a space for extra ads on my app, so I install StartApp banner and the PPC is about $0.002.
I think that this rate is very low. So, I’d like to know more profitable banner mobile ads network.
Thank you.