Results seem to vary considerably depending on the market and keywords, although it does seem that with some patience and experimentation you can find that high value/low cost sweet spot.

They key is patience. I had tried Facebook Ads several times to no avail, but after reading one of your blog posts as well as several others, I went back to the drawing board until I started finding the variables that made it work. I'm hoping this post expresses some of the lessons learned.