There is a lot more room to "deal" with new cars than used, unless the person who traded it in really took a bath. These days you can usually see what the trade-in value really should be and you can get the dealer close if you're buying another car from them. So depending on what the dealer paid for the trade, he might not be able to go any lower. Did you pull a value for the car in question from KBB or Edmunds? Are you way under what the value is?