Another few things to consider.
Be honest with yourself & determine what condition you believe the TT is in. Is it below average, middle road or above average condition ? Condition of a used RV is a major factor of value.
Also, If you trade it in, do you pay sales tax on the difference? If you sell it yourself, & purchase new without a trade then you'll owe sales tax on the total purchase price.
Another factor is "regional" value which NADA doesn't consider. An example is here in Idaho, the value of a good condition POP-UP = NADA HIGH + $1000 = what it can be sold for. I bought & sold 6 of them & paid cash for my hard side with the profits.