Let's say you get 4,000 impressions on a given day in Adwords.
With a CTR of 2%, you get 80 clicks.
But if you can bump that to 3%, you get 120 clicks.
Let's say you've got a CPA product that converts every 20 clicks, paying you $30 bucks. And let's say you pay $.5 per click. That means when you spend $10, you make $30.
So with 40 additional clicks, you've got an additional $60 bucks in your pocket - for 1 day. And that's on top of what you made from the rest of your clicks. And obviously the theory remains the same when you scale your campaigns up.... you can see how increased CTRs can mean extra bank for you.
I've tested this and it works. So try it out and enjoy your higher CTR's! Best of luck.