By tracking people that converted and then feeding that into Facebook's Lookalike Audience we were able to drop the cost per lead to about a third of the original cost over time (from $78 to $27). It beat everything else (TV, display ads, retargeting, SEM, etc), to the point where we only did that.
We've noticed that every time we stopped the ads, or changed the targeting parameters/audience, it would take a while for Facebook to get back to the same results.
p.s The lead cost was that high because we were selling $200k land + $500k houses from a small tropical country to US consumers that may have never even heard of that country.