Two things.............
If I have a Nikon scope, and if it goes kaput, the chances are very good that I'm going to be needing another scope, not credit at the Nikon store.
Secondly, I happen to like Nikon scopes, especially those with the BDC, but the fact that they are no longer made or under warranty means that the prices that you see some people still asking for them seem very unreasonable.
