Respectfully disagree. I mean you are correct- I'm aware they're quite expensive - licensing audio is often way more than licensing video or other media... but as I've lobbied for in the past; don't underestimate the impact a fitting soundtrack has on the overall game. BaD, LoF, COBD, and others have their success in no small part to their soundtracks. Without sound games can end up feeling lifeless, even with the most gorgeous artwork, it feels kinda robotic.
And as for the setting dictating an audio style - that's up to the dev/artist to determine; often the audio style determines while the setting follows. The game could certainly feel very different given two different soundtracks.