TT depreciation per year according to kbb? Cargo trailers

I have owned several enclosed trailers that I've used to haul snowmobiles, but are capable for many uses. They hold value much more than TT campers. My 7x23 enclosed that I have now, could easily be made into a toy hauler camper. It is all aluminum, including the frame, has a 3,800 lb CC, and has finished walls/ceiling.

Jerry