When it come to dealership margins, no reasonable consumer wants a great dealership to go out of business. It really should not be a factor.
If one nets out to pay as low as MSRP (including taxes & everything), you should be happy. Although it may take GM incentives to do it on certain vehicles sometimes.
Otherwise get a Scotia GM Visa and diligently use it to earn GM dollars.
I have redeemed over $12000 since getting the card. It costs me absolutely nothing, it has no limits and it knocks a good chunk off the vehicle purchase.
If financed, negotiate the lowest interest rate possible. I have three vehicles at 0% - and yes, I would have saved a bit more if I had a higher interest rate.
Strange how things work ... affordability matters but how much someone "saves" does not impress me the most when they are showing me their New Corvette.