|Flashlights have same use effect as Elune Stones.|
Image credit: Vinogradina
Easy and profitable to create
Not only is it cheap to create High-Powered Flashlights, but trinkets have always been equips that sell the fastest from my experience. Most players have empty trinket slots, even though Cataclysm added some trinkets to quest rewards. Still, these are blue quality and offer the most important stat in the game: Hit rating.
Even though they are Unique-Equipped, often a single person purchases two of them. It's a good idea to sell multiple of these items, but no more than 3 at a time.
High-Powered Flashlight (250 Engineering)
Thorium Bar and 1 x Runecloth. If you have mining, it's often more profitable to purchase Thorium Ore instead, and smelt it.
No Flashlights available
Even the larger realms have usually zero sellers, allowing you to choose freely how much you charge per High-Powered Flashlight. However, I wouldn't go above 300 gold. Experiment with the prices to see how you make sales the fastest.