Sorry, but it seems like they saw you coming a mile away. Buyers need to do their due diligence. A salesman and company is out to make as much money as possible. A buyer should be looking to get the best deal possible.
The OP should have known if he was getting a fair price or not. If the trailer costs the dealer $27K, he should have known that a $24K price is absurd. If EVERYONE is selling that model for $28.5K and you get a quote for $24K... something is up.
If the OP doesn't have a signed sales contract, he is promised NOTHING. All the emails in the world don't mean a thing.
If the OP got strong armed into paying too much, or more than he wanted to, that is on him.
It seems to me that in the 6 weeks between the promised date of delivery and the actual date of delivery he probably could have found another dealer that sold the same trailer.
It seems to me that I would know my floorplan in and out as well. Especially if I had to wait 6 weeks after ordering it.
I hate to sound like a meanie pants... but come on man, you gotta do your due diligence or expect to get spanked.