'Philngruvy' - The $200 gestimate is simply my conservative estimate, based on observation over time, a bit of knowledge, and opinion.

Your desirable model 1901 carbine sight is the most common of the U.S. Krag carbine sights. I have seen nice specimens of the rarer model 1898 and 1902 carbine sights available for around $200.

Strangely, the model 1896 Krag carbine sight, which should not be all that rare, is in high demand and when available will bring $500 to $600.

In the end, it is all about demand and what someone is willing to pay.

I have no wish to rain on anyone's parade. Maybe $200 is too low a value for your carbine sight, but, $550 seems too high a price for the 1901 carbine sight.

I am glad you were successful in a gun auction. That .45-70 should be a lot of fun. Getting a valuable carbine sight is a great bonus! Enjoy!