I didn't see anyone else mention it before now, I'm surprised.
ICv2 just released its top 300 comics list for September, which includes everyone's favorite "tentacle rape" issue of Heroes for Hire.
HfH#13 comes in at 40,086 copies sold and sits at #51 on the list.
HfH#12 in July was at 41,229 copies and was ranked #64.
While it's true that sales dropped a bit (1143 copies), its ranking rose. And there's a fairly large difference between the top-selling item in July (Thor #1, 165,325 copies) and September (World War Hulk #4, 148,610 copies), and I wonder if sales weren't generally a bit down for last month, or if perhaps it's a result of there being no super #1 debut/death of iconic hero to buoy up the month's sales. (After re-reading that, I checked: in June, HfH #11 was #53, at 41,298 copies, and WWH#1 was at the top, with sales over 170,000.) Another contributing factor to the slip may be the gap in publication (no issue in August).
Results, therefore: inconclusive. I can't point to the comic and say, "see! boobies and bondage sells!", but on the other hand, it's hard to make a definitive claim like "see! gratuitous offensive sexist material kills sales!", either. I don't think the losses are really all that great. One might speculate that any loss of readers from offense was offset by gains from drooling fanboys, although that would have to assume that those feeling offended actually were buying the title in the first place.
What may actually be the case is that for most comics buyers, having a bondage scene on the cover isn't really all that important an issue either way.
What may be a contributing factor is CONTROVERSY, CONTROVERSY, CONTROVERSY.
Because, May? Ranked #109, with sales of 20,503. Sales after that month doubled. And when did the whole cover controversy break, again...?
Okay, an edit because I'm a moron: of course, it's the World War Hulk tie-ins. dur. With that factored in, even controversy as selling point becomes questionable.