TT depreciation per year according to kbb? Cargo trailers

Yup, your comparison is not valid.
RVs depreciate like mad. Cargo (and other) trailers don’t.
Think they’re expensive in Iowa, look out here where it rains all the time.....
For new trailers in your neck of the woods, King Company in Wausau WI was the best price/value IMO. Bought a cargo trailer there a couple years ago.
To compare how much value they retain, I used it for 1 trip back to WA and sold it for considerably more than I paid new.