Why would a state register the vehicle for half again more than the factory GVWR? Easy answer: more money for higher weight fees.

Highmark18, I think you have a good case to change the registration because your registration is clearly out of whack with the factory information on the vehicle, but you may need to talk to the supervisor or even "shop" for a DMV location that is sympathetic. (They will not want to lower the weight fee -- it is $$$ that they get every year.)