I doubt it is a 6.5X16. Maybe you meant 6.5X20. That being the case, pricing is going to depend on reticule and tube diameter. A 6.5x20 40mm in 1 inch tube with a standard duplex cross hair is about 700.00 new. 50mm is probably going to add 70.00 or so to that price. If it is a 30mm tube price goes up again, as does certain reticules. If it has an adjustable objective the price will also be higher. These are new prices and should be reduced by 30% or so used, depending on condition.
Bill