About $1,800 is right.
Used Mark 4s, 4-14ish go for about $1,000. I got a 6.5-20 TMR w/ Illum Reticle for $925.
A Remington LTR new is about $947, a 15-20% discount for used guns and you have approximately $800.
You would probably get more for the gun if you parted it out.
Most buyers wouldn't want that exact scope, or that exact gun, or that exact ring and base, etc. etc.
If you sold it as a package deal, I really wouldn't look at it beyond $1,500, unless you showed me how tight the gun could group.