That is a perfectly reasonable question. I didn't do any testing -- it was an experimental campaign and totally flamed out. If it had been anywhere in the general ballpark of feasible, I would happily have started iterating, but $35 CPA to the free trial of a thirty dollar product did not strike me as something which was amenable to iterate-quickly-to-victory.

For both the Theory of Geek and CoderStack ad campaigns going from initial ad to an optimized ad dropped eCPC by two orders of magnitude. Optimization has a huge impact on Facebook Ads.

Although if you're paying $0.05/click for traffic on Google there's probably less upside for you then someone who's paying $0.50/click on Google.

I second that. Just changing the image will often swing CTRs wildly. One of the great things about FB ads is that you can put an image (unlike google text ads) and the audience responds very well to images.

Have you ever considered setting up an affiliate program and letting other people risk their own ad spend? Also gives the teaching blogs incentive to promote it to their readers/email lists.