Unless it is a Leupold, Zeiss, or other better known brand a scope adds very little if any to the price. Sounds like it might be an older Redfield. If so it would add $50-$100 to the price.
The pushfeed XTR's are good dependable guns, but can sometimes be hard to sell and don't bring as much as they probably should. A good thing if you're a buyer. I think they are the most under valued used guns out there.
Depending on condition and chambering $300-$400 with around $350 on average is what I see them actually sell for. I see a few advertised for more, but they aren't selling.