"problem" is that all important big sales where done before or shortly after release (big resellers like amazone and so on), so the "modding benefit" regarding sales is only for customers who belived that the modders will fix it anyway and couldnt wait to have a look on it. I dont think that resellers take modding possibilitys or modding expections into account while ordering but mod expecting end customers do with pre orders maybe, but this seams to be only a hand full.
modding efforts through the community together with modding possibilitys duo the product itself can help rising a bad product repurtation maybe for the next title (the price is allready to low for getting a reasonable profit from the current title), even if it is a failiure for us "sim`s" at release, this customers can expect the fixes they need from the community later, some curios buy at release of the next title (me for example)... but those most "important" casual gamers will buy it anyway, because they know they can expect an unfinished casual game for idiots (and they are proud about it), willing to pay the full price at release (this nature makes those customers so important)
