Just because the used ones with low mileage are asking for this amount of money doesn't mean they are going to get it. The can ask for the moon but it is only worth what someone else is willing to give. Also lots of people are upside down on their loans and need this amount to get out of their loan without having to pay more money to sell it.
If you could do this you would be a very lucky person and go and buy a lottery ticket for the next big jackpot. Then when you win that you don't need to worry about it. ;)