The 58 is an interesting shotgun. It's been greatly improved on by subsequent designs like the 1100, but it still has its fans. It'd probably be worth $200 to the right person if it's in good shape, but you'll want to make sure it's in good shape. I've heard that 58s weren't the most solid autoloaders, and things tended to break if they were used heavily, or an owner didn't understand how to properly operate the manual gas system. It'd probably be smart to have someone who knows what they're doing look it over for you.
One neat feature of this model is that you can take an 870 barrel, drill gas ports into it, and use it on a 58.