I'm going to disagree. My agency helped take one of our clients to #1 grossing in education off the back of mostly facebook and twitter mobile install ads. We had an average of $0.60 to $0.80 downloads with an over 10% conversion to our $30 paid version.

I've also tried some things that don't really work on facebook at all. I think as marketers, we need to be nimble and quickly figure out if a given platform is where our audience lives. Iterate quickly and do statistically relevant test sizes before you commit a massive budget to anything.