They are worth something to someone. First thing is to clean them up. How many miles have they done? Is their any oil along the piston rods. Are the piston rods scratched? Where the dampers giving any cause for concern? Why did you remove the Dampers? Collapse them completely and pull out the full length a few times. Does each pair feel similar? Do the adjustments work, does it change the rate of damping and is that similar across a pair? If all is good then they may be OK. On the hardest setting they will feel incredibly stiff and very difficult to extend. KONI dampers can be rebuilt. Ask how much that might be to service them if they appear degraded or vert high mileage.
Then put them back on your vehicle, it would be very difficult to buy better unless buying new. Sold your vehicle, put them on the next one. Don't have a suitable vehicle. Chose a friend who may need them if you do not have one sell them on here! Do not junk them!!
