I think by simply joining Facebook groups in this sector and engaging with the group you could've achieved 600 likes in the same timescale and saved yourself the money.
We use Google mostly for adverts, and we're showing about a $1 per user acquisition rate. That's not CTR rate, that's
clicked ad->saw site->signed up.
At almost $2 just to get a "like", I would be very hard pressed to justify that.
"we averaged $1.83 per 'like'"
"what's a 'like'?"
"somebody click the like button next to us in Facebook"
"how much money is that worth to us?"
"well, it identifies interested people in our service who we can advertise to later"
"so we now know about people who might be interested in our service if we decide to spend even more money advertising to them?"
It seems like you can't really judge how much you should spend per like because you haven't yet calculated the revenue and profits per like.