We know the benefit of each marginal IQ point is something like a few thousand dollars in lifetime income
~1% income boost per point. See this report for an almost identical analysis of the benefits of programs to prevent low birth weight. With very low discount rates/return on other investments they estimate a value of between ~$3k-14k for each 1% increase in earnings. By that metric (and metrics used for preschool interventions) it should be cost-effective in a few years but is not so now (particularly in the absence of any clinic offering an organized service).
If one has a higher discount rate (they use rates of 2-4%, and wage growth rates of 0-2%), like a typical parent, then it would not be appealing.
On the other hand, this isn't taking into account non-wage gains (health, longevity, institutionalization, marriage prospects, well-being).
Well, one problem with simply regressing IQ against income is that to an extent the gain is coming from what look like positional or zero-sum effects like displacing someone at an elite university; that's one reason I've been compiling relevant papers for a while at http://lesswrong.com/lw/7e1/rationality_quotes_september_2011/4r01 I am more interested in the marginal increase in net societal wealth from IQ; if all IQ does is help on play games better, it's not something I care about increasing.
...By that metric (and metrics used for preschool interventions
The article by Robert Sparrow:
Quote:
The possibility was discussed in MIRI's "Uncertain Future" toy forecasting model back in 2009, and the analysis formulated a few years before that.
ETA: And further discussed in James Miller's recent book, "Singularity Rising."