Even if they play games with the auctions to keep the price up, at the end of the day X company is spending $5 per thousand clicks (or whatever) because they think it's worth it. Google can charge whatever they want, they run the platform, and it's not as if anyone is forced to use them.
I just don't see how you could in the same breath (how the government basically has) that the app store isn't a monopoly, but Google ads are. There's other ad companies, there is no other way to get an app on iOS.