Then someone needs to come up with a way to answer the question "did i get a good deal" and not hurt their feelings with the answer.
The good deal is directly related to how much you paid. If you didn't pay cash or take 0%, then the interest you pay over the life of the loan has a HUGE impact on your cost to buy that car.
And dealers will lower price if they know you are financing through them. And shouldn't the origination fee be factored in?
Sorry, but if someone doesn't want to share how much interest they are paying , then they should not be asking if they got a good deal. Generally if they financed through the dealer (not Mazda) and paid more then 2% interest and an origination fee, the answer is "No, you didn't get a good deal, no matter the sale price and rebates".
If you think that is harsh, then just talk about monthly payments, don't ask what options they got, and don't ask months of loan either. So then the guy with an 84 month loan on a Sport, got the best deal as he has the lowest monthly payment. That makes as much as sense as not factoring the cost of the loan in the purchase price.
"did i get a good deal?" on the vehicle is completely separate from whatever financing rate a person qualified for. What if someone has really bad credit but a lot of cash on hand, and can only get an 18% loan? They might pay it off in a few months and end up paying almost no interest. Did they get a good deal?
Also, not all parts of the country have the same rebates available at the same time