Oregon plates can be kinda expensive the first year. They also frown on very expensive RV's with several at the same address.
Oregon has a per foot charge the first time it is registered in OR. Mine is 31' long, and I forget how much it cost, but something like $300. The plates are two years for much less. You should probably call and tell them your RV has a GVWR of 54,000 or whatever, and see if it is extra expensive because of the weight. I have a shuttle van, and it is $575 a year because it has a 14,500 GVWR, but by changing the licensed weight maximum to only 10,000 pounds, it went down to what passenger cars pay, $126 per two years. Much less than the commercial truck fees!
Good luck,
Fred.
