Quality content is what drives traffic to your site, and the better placement of ad can return much more than the cost of your labour.
What I mean to the better placement? You can put ads on a page anywhere you like, but it will not help you until your visitors notice them. The most common ads place is at the top, which pays you high. But as you know, Google Search has added a new algorithm, which checks layout of pages and demote those sites that have only ads and not much content "above-the-fold".
Here is a video shared by AdSense team on how to best implement up to three Ad Units for Content across your content-rich pages. It makes a balance between optimization and revenue.