Including ammo I would guess the price somewhere around $500.
I remember guys buying new ADL's for donor actions for around $350 just a couple of years ago. Rings, bases & scope usually fetch around 40% - 50% of their new price. Ammo is a WAG at $10 per box of 20.
$350 + 75 (rings, bases, and scope) + 70 (ammo) = $495 if my math is right.