My response:
It's highly doubtful that a dealership would advertise without a "disclaimer"; however, I'll presume that you're correct about that issue at this point.
But, without much more specific information (your post was very general, and without specifics), I would have to say, in my opinion, that a $5,000.00 price differential would qualify as a "mistake" and the law would not enforce a demand on your part. If it had been within a few hundred dollars, or even a thousand dollars, I would tend to favor your position. But, $5,000.00 is a bit much to hold their hands to the fire.
Good luck.
IAAL