Assume (as DC seems to do) that no female reads Batman; this means that about 70K males do (I'm using March 2006 sales data for everything), out of a total universe of DC buyers of 200K (the sales of Infinite Crisis; sadly, that was by far the best seller, so it makes sense in a handwaving sort of way to use it as the total population size).
Again, let's use DC's apparent idea (otherwise ASB&R makes no sense) that no woman reads comics. As, on the other hand, women can read comics (cf almost everybody in my f-list), we can handwave away gender-specific factors and argue/model/assume that there are 200K potential female buyers of Batman who aren't buying any comics right now.
Lets introduce the revolutionary concept of level of cooties in a comic. Assuming -yes, as DC seems to do- that there is an inverse relationship between what male and female readers want (in few words: no, DC, there isn't), we say that a comic has a level of cooties k (k between 0 and 1) if it has enough "girlie stuff" to make a proportion k of the potential female readers buy the title, and a proportion k of the male readers drop the title and step back in horror. (The symmetry of the assumption looks very implausible, but consider the counterproposition: it means that female readership could be raised without losing any male readers - which is exactly my point anyway.)
The key observation in the model is this: there are more women not reading comics (in this model) than men doing it, so raising the level of cooties gives you more readers in the aggregate. Say your level of cooties is k = 0.1. Then 7K of your 70K male readers will be off in the forums screaming (very manly, we hope) at you, while 20K females will pick up the issue, for a net gain of 13K readers. Sweet.
For symmetry reasons, a reasonable equilibrium point is to aim at having the same number of male and female readers (this assumes that the maximum level of cooties in a particular comic book is about the same as the maximum level of boobs or attractiveness to males; not a more unreasonable assumption that everything else here). We do a bit of algebra and arrive at k = 0.26 approx. At that level of cooties, you lose about 18K male readers, but win over 50K female readers, for a net gain of 32K readers, or about a 50% extra readership - my figures in the last post were off a bit (note to self: don't do this while asleep).
(ETA: A non-symmetric aim -as many women as possible- would theoretically raise total readership even above this number, although then arguably you have to consider second order effects, and in particular the convexity of the boobies as a function of cooties *is twelve*).
Anyway, 50K extra readers at USD 2.5 per issue is USD 125K per month, or USD 1.5M a year. With bank deposit rates at perhaps 6.5 points a year, this is equivalent -over the long term- to a single payment of about USD 23M, which is an estimate of how much free extra money they aren't bothering to take out of fear of cooties.
Ah, but then, DC/Marvel aren't about the comics these days, but about the movies, right? According to the trusty internet, Batman Begins grossed USD 370M. Using the same set of assumptions about cooties and such, if the Batman title were optimally female-friendly, the movie would have grossed USD 555M dollars - an extra USD 185M. Plus the USD 23M of comics, we can headline this at a nice-sounding "more than two hundred million dollars".