Building salvage has been around for a while now. I dabbled in it in the late 90s early 2000s when it was really popular and competitive.
Still a fair bit of it going on but the best barns/buildings have been pretty much picked over. The value is in the type, quality and age of the materials in the structure. In the east the buyers are looking for big beams of old growth pine, especially heat of pine and if it can still be found chestnut. Chestnut beams command big bucks. This is used to be re-sawed into flooring. The wider the beams the better and how they were milled.
Wide thick siding in good condition will get attention also. Along with some of the structural components. Like loft flooring in decent condition. I don’t think any salvage companies would be much interested in sheds small structures unless they are made of really quality wood.
Some of the barns, building I looked at had some very tasty/appealing wood and other tidbits. But the owners were hallucinating on what they thought it was worth. HALLUCINATING. I think shows like Barn Builders and others of the like that have gone around over the years had a lot to do with this. (a bit of BS goes with these shows) The owners had no idea of what it takes, time, effort, equipment, labor costs to dissemble without making firewood/kindling out of it. Then it has to be sorted, cleaned of nails etc, milled and marketed.
House, architectural salvage is the same. Quality and age of flooring, attic flooring, doors, trim etc dictate the value. 1700s, 1800s early 19th. Old window glass can bring a premium.
Unless the building is a “gem” most will offer little to nothing other than picking it apart and demo the rest. Saves money on paying someone else to do. Dumping fees and hauling is not cheap. The less you have left over the better.
Beware of amateurs they may leave the site a mess and expensive to clean up.
Some local fire departments might be interested in doing a controlled burn for teaching purposes.
Depending on things the cheapest way to get rid of is to burn and bury. Some Fire departments will over see the burning to make sure things don’t get out of control. They may do this for free or a small fee.