Colorado's registration fees are based on the value of the vehicle, cars, trucks, trailers, street legal motorcycles, it doesn't make any difference. When I registered my trailer (2012 Voltage 3200) in 2011 as a new vehicle, I think I paid about $1,600 for the first year. Last year my registration fee
for the trailer was about $330, so the fees decline fairly rapidly, as does the value of the trailer (ain't depreciation wonderful?). At some point, the registration fees will bottom out. For my 2002 DRZ 400, that is now about $58 per year, I don't have any idea what the bottom will be for my truck or trailer, assuming I keep them for 12 or 15 years. It costs to have toys in Colorado.