agreed it's a no brainer new even in my mind... but comparing it to a used one (which is how most awd good sized sedans are purchased in the retail world), a comparable g80 is over 15k more than the charger... then, it's a whole new debate and not something that gets cross-shopped.
as for the who it's for... heres what a salesman *should* be telling you for each point you made; performance wise, the v8 is a great option, but a) it's not available out of fleets and 300hp is all you need. the 3.6 also has a lot of potential for tunes and such. fuel economy, I was able to eek out 8.3l/100 out of the same drivetrain in one avg, so it's possible, plus, it uses 87 octane, unlike most turbos in the category. overall, getting a1 year old example with lower kms will net you a lower price point, plenty of hp, and more room than nearly anything you can compare it to. plus, looks damn nice and while some might say dated, it actually still holds its own against nearly any in it's direct competition for infotainment and all that.