Then take the success probability and multiply it by the value a woman would expect from being free of PPD. I'd wager it's still considerably higher than $16k.
I'm noting it's less clear than other expensive things like the meds that cure hep c. In that case, you're weighing the cost of a near certain cure. I've not seen any sort of depression med with that kind of clarity of effectiveness.
The FDA's press release didn't say anything about the success rate, only that the test group had significantly lower levels of depression than the control group. It's true that a lot of antidepressants fail to improve symptoms in a lot of people. The effectiveness of this particular drug better be outstanding, otherwise Biogen-Sage won't be able to justify the high price compared to other antidepressants.