I make the Sinister Combatant's Intuitive Staff (https://www.wowhead.com/spell=282343/sinister-combatants-intuitive-staff) for 20,000g and the materials are 13,000g or less. This makes a single expulsom worth 7,000g, plus or minus a few hundred due to the staff's deposit, AH cut, returns, and variance in materials. It still remains well above 5,000g and I think some people buy and resell my staves because the secondary stats matter.
If you find yourself coveting your first mount, and with no money to purchase it, try to swallow your frustration and work at earning and saving up so you can buy it honestly. Nothing is more annoying to other players who are working hard to earn their own money than hearing someone begging for gold so that they can buy a mount or fancy piece of gear.
As a hero of the mighty Alliance, journey to the seafaring kingdom of Kul Tiras, home of Jaina Proudmoore. Untangle a web of betrayal and dark magic as you encounter power-hungry pirates, witches wielding death magic, mystical sea priests, and more. Explore the stony peaks of Tiragarde Sound, trek across Drustvar’s high plains and red forests, and navigate the intricate inland canals of Stormsong Valley as you convince this fractured kingdom to join your cause.
The most simple thing is TradeSkillMaster. This AddOn shows you quite an amount of information in the items tooltip. In my opinion, DBRegionMarketAvg the best source. It tells me the price, an item was posted on all EU realms in the last 14 days. Why not DBMarket? DBMarket only shows you the items value from your server in the last 14 days. This value often gets manipulated. Some people start to post an item with a 500g value for 500.000 Gold on the auction house for several weaks. As a consequence, DBMarket is rising towards 500.000 Gold.  If you use DBMarket with 100% and post your item for 500.000 Gold, nobody will buy it.