Price range can vary according to the following:
If the projo is fired or unfired.
If it has original paint and markings.
How rusty or beat up it is
If it is relatively rare versus more common.
The condition of the nose fuze, beat up versus unfired.
If it is complete and fits together nicely, versus missing fuze etc.
and most importantly your selling environment, militaria/gun show versus flea market in an antigun state.
That all being said, if it has all parts, fired and fairly well cleaned up, start at $35.00 for the projectile and go up as conditions improve, or you could go lower if you become desperate.
A brass cartridge case for the same round could go for $35.00 on up also depending on condition, rarity, etc.