The info on Quattro's pitch is pretty interesting. Thanks for sharing that. 11 out of top 40 uses them and who knows how many used admob or another ad network. Only a few top ranked apps happen by chance anymore is my guess.
I still think ads are an expensive and impractical way for most of us to even attempt.
If it comes down to it, I agree investing in better graphics will still pay off the most. It's so easy to offshore work now that getting decent graphics is a lot less costly than people think. It's been mentioned many times before: icon and screenshots are what people see first. If they don't like the way it looks, they won't even bother clicking. It's been true since day 1 of the app store. We got Mini Touch Golf's splash/cover art designed for $50 in 2008. Then just shrank it down to make the icon.
Nowadays, I spend more on graphics but I got Sniper Strike's new icon redesigned for $50. I first went with a cheap route and just shrank my cover art down to size, but I think that cost me quite a bit by having an unattractive icon. Impossible for me to prove, but I think I didn't take full advantage of my opportunity when it was on New & Noteworthy.