Hmmm....I would contact the dealer and give them h#$l.
When we ordered our trailer we paid $650 for freight, so I am sure your dealer has charged you with it also. Its not your problem the gas prices went up in the meantime, and they should have forseen this anyways, and maybe raised the freight charge a bit initially.
2010 Dodge Ram 1500
2012 Rockwood 2306
DH (Alan), DD (Madison) and Zoey the lab,