only the manufacturer knows the true cost of the car. it gets confusing after that. even with the same sales person, (s)he can change the freebies list by the hour.. my only advice to you is, get several quotations and see which offers the better deal. you can pit them against each other. maybe you can even play poker by claiming "SA says he can give me this... can you better his offer?"..
but keep in mind: nothing is free. what SA gives you with one hand, he may take away in another form with the other.. you have to do your math.. literally.
you think this is confusing? try buying a car in the states!