the beef is against buying your brand keywords. I've always found brand keywords to be the best CPA though - much lower than non-brand. plus, you can cookie returning users and take them out of your conversion calc to see exactly how many new customers you are getting and what it is returning you. maybe it is just that google ads are expensive and competitive and there needs to be better alternatives to reaching people. I've yet to have great success with FB but still working it cause I want alternatives.
I've heard Facebook is cheaper but haven't seen a comparison on effectiveness yet. We're actually about to try a Facebook campaign. Would love to hear what you're trying and whether it works.