Thanks Laura for the comment and link. Yes, I think that the studies' approaches to cost-effectiveness were quite fragmented and it'd be important to standardize and nuance them further, e.g. drawing from methods applied by Caldes et al. (2006) in World Development and earlier work by David Coady and others on Mexico. I like the way you summarized some of the tipping points, it would be great to examine them in a comparative mode.