Well I will have to negotiate my trade in but its a older model GM truck so I am pretty sure they are all going to give me the same amount for it
I used to be a CFO for a fairly large automotive corporation.
Profit margin on new vehicles are low. Depending on make, the average is about $1200 per vehicle. Dealerships make most money from co-op money from franchises. More inventory they move, more back end money from factories.
So, if you want the rock bottom price for a new vehicle - go to the largest dealership in your town or next town on the last day of the month, on the last hour. Dealers have extra incentivized rebates in their desk drawers for such customers (app. $1000-$1500). Depending how close they are to their annual quota, they can dig deep into their profit margin (I've seen plenty of $5000 losses on deals).
Now if you're looking for a used vehicle - don't go to a franchise dealership. Used car profit business is the icing on the car at a franchise store. Buy from an individual and never ever buy from an auction. Wholesalers know how to cut corners and make check engine lights disappear without doing the service work.