OK, provocative title, and I guess anyone who is making decent money from AdSense can reply. Let's set the benchmark at anyone who is making more than $500 per month on a single site from AdSense. Kudos to you if you are.
Here's the question, it's really simple.
Once you've found a keyword niche that you believe pays well, and you setup a blog with AdSense, how many posts do you need on the site? And does the quality of the post/content matter? In other words, do you employ cheap writers to write 40-50 posts in the niche, and you don't care about the quality as long as the keywords are in the content, or is it more involved than that.
Forget about backlinks for the moment, let's just focus on content and keywords.