How much is a Besson 2-20 trumpet worth in rough shape?

It depends on the specific condition and age of the trumpet, as well as the location and market demand. Generally, a Besson 2-20 trumpet in rough shape can be valued anywhere between $500 to $1,500. It's important to consider factors such as whether it is playable, the extent of the damage or wear, the presence of original parts, and any repairs or modifications made to the instrument. To obtain a more precise estimate, it is recommended to consult a professional instrument appraiser or visit a reputable music store that specializes in brass instruments.