...what is the problem? You don't like extra exp, even if it's small? Treat it like quest then. "Collect some spears for me I take them all".
Than it should be made a quest, repeatable and with a cooldown.
I haven't done any repeatable quest, but the cooldown should be the same.
Either that or increase the amount of (sharpened) spears or change the items needed every time you do to quest.
Change of items could involve junk and things that are made mostly out of junk: BBs, radios, brass knuckles, spiked knuckles, shovel, old shovel, extended magazine, speed loader.
That would make the quests similar to the 'Bring items to Monte Carlo' quest in the Boneyard.
Reward could than be changed to an amount based upon the amount and item you need to bring.
It should stay less than than when selling it to a trader as you also get xp as a reward.