Yes, bikers should contribute, but the cost to make and maintain a bike path is minuscule compared to a road that can stand up to tractor trailer traffic. In the overall scheme of things, I think that the amount I pay in taxes more than covers my road use on my bike and an additional surcharge is unnecessary.
In terms of overall costs, the cost to public health and the environment is much greater from car usage. The increased use of bicycles would actually save the state money in lower healthcare costs and lower future maintenance costs and unforeseen environmental cleanup from the vehicle pollution.
Its a $40 tax ($1000 bike), one time, on new bike sales. Bike road maintenance isn't just from bikes doing damage, its from environmental damage. Think of painted lines, pot holes, cracks, frost heaves etc.
When cars are taken off the road one day there will still be costs to maintain bike paths. In my home town we have bike trails, only used for bikes, and they have budgets for keeping them maintained. They're pretty cheap, $40 goes quite a ways, and that's on a bike that should last 10 years ($4/year). Does Oregon not have a single dedicated bike lane that is separate from the car lanes that you could get the annual cost for?
I understand everyone wants a free ride, but its hardly going to change bike ownership rates.