When I moved to Oregon in 1979 people would come from out of state and buy an RV, pay no sales tax, get a PO box and register it for 2 years for twenty bucks. There was a strong dealer base of RVs and people would fly in rent a room buy their rig and drive it home while spending a bunch of money in the state. Oregon felt cheated and put a stop to it. Many dealers went out of business.
If you buy a truck in Oregon and pay no sales tax and drive it across the river into Washington to register it be ready to write the check.