Think of it this way: Magic users make up maybe 1 in 1000 people. Those magic users with the skill required to make magical items are maybe 1 in 100 wizards. So there is really only 1 person capable of making magical items for every 100,000 people. It is therefore pretty logical that magical items will be reasonably rare.However beyond the basics of healing potions and magical swords there is also extremely powerful magical artifacts. Think Excalibur, the Holy Grail, the Ark of the Covenant. Not just magical, but ridiculously powerful and important objects are a theme in many fantasy stories. eg. The One Ring to Rule Them All, The Deathly Hallows, the Elder Wand, Mjolnir, Balmung, the Green Destiny.
However it is strongly recommended that artifacts not be used as the basis of a short story. Something that powerful deserves a fully length novel as there will usually be multiple parties seeking the artifact and want to steal it and use it for their own purposes.
Artifacts will also be famous or semi-famous, so expect the characters to know at least something about such legendary magical objects.
EXAMPLES
The Backlash Spellbook, also known as the Tome of Havok or the Tome of Chaos.
Created by a group of powerful wild mages it is a powerful artifact that any wizard or mystic may use to unleash powerful magical spells. Unlike normal spellbooks wherein the reader must memorize the spell, the spells in this large book can be cast simply by reading the spells aloud (and pointing at a target in some cases). However the unusual spells in this book often have a tendency to be disastrous and even backlash against the caster. The tome is written is elvish, so any arcane magic user that can read elvish is able to use it. The spells in the book often have names that sound very powerful. ie. Acid Tsunami, but the wave of acid goes out from the caster... and then comes back!
The Book of Saraz:
This book contains dark knowledge and forgotten dark magic, but it also contains a magical recipe for creating multiple stone golems. The book is also said to contain the knowledge needed for bringing the Dead God Saraz back to life.
The Staff of Moonlight
A powerful magical staff said to have the ability to heal people and rumoured to be able to bring people back to life. According to legends the staff disappears whenever it is used to raise the dead. The staff is holy to the goddess Metrequia.
