This is fiction there really is "no line that cannot be crossed". What I do see is an incredibly lack of taste and hack writing at it's finest worthy of Kickass 2. Basically Paz being tortured in various ways could have been changed by a dog and the message would have been the same "the villian is very bad", because for Paz (must be feeling clever for calling her peace in Spanish...) it's never analyzed how this actually affects her.
Basically, this is not being "adult" or "dark", this is being juvenile and 90s comics edgy all over again just because you can. Basically, if you want to tackle the heavy stuff, you actually have to tackle, it, yes there was "torture" in MGS, but aside from not even getting the insinuation of Meryl being raped (which again adds nothing outside of "OOOH LOOK THEY SO BAD!" since physically and mentally she clearly doesn't seem any worse for wear), the torture we see is cartoon torture of being strapped to James Bond devise, after the session Snake is right and chipper so it's not like it ever had the balls to deal with the aftermath and certainly with the tone of the game it didn't seem it had to go nowhere near there.
Want to see something adult? Read the latest chapters of Attack on titan manga, [SPOILERS COMING] we had a secondary character tortured to death only to have a few chapters later, two prominent main characters torture the other torturers to get information, while being quite graphic, but more importantly, while making it very damn clear what the sequels of it for the tortured and how incredibly low hour "heroes" have sunk for it. There is also the Berserk manga where you get to see the brutal consequences on two main characters of rape, leaving tremendous mental scars on both, one becoming a violent frothing mess of a man and the other becoming a catatonic woman that can't deal with reality anymore.
Basically, if you want to add real life horrible issues, tackle them head on and to the end of it, if not, its just shock value and has no worth except for making kids feel all manly and say "I play adult games!".
As for the price thing, nothing else to add, its bullshit pure and simple, I mean, I'm glad people could enjoy it but anyone who bought it has to understand that is the reason a publishers know they can get away with this shit. We, as consumers, have to be responsible too if we want to get the best for our buck.