The fact that they were found in a dumpster should be a good indication as to what they are worth.
I bought a b-square scope and mount off of ebay for $50. The scope was a Sun Optics. If you look a few threads down, someone asked about Sun Optics. Basically, you get a free scope if you buy the mount. I don't know if the scope you have is Sun Optics or not. Cabelas and Bass Pro sell the combo for $100.
I would make sure the scopes are not broken before giving anyone any money. If they are not broken, I don't know how long they will last on the rifle you want to put them on.