In the one minute it took you to find and purchase that item, I used an AH in another game to purchase a full set of gear and list my old stuff.

The thing is, market wards have zero advantages over an AH. They do nothing of value that an AH does not do better. Nothing.
They don't list a price history. They require you to run around to buy or sell anything. They essentially tax random items because it's quite unlikely everything you want to sell will be in the same category. They force you to sit through a loading screen and wait for a bunch of NPCs to load for each item you want to buy. They are enough of a bother to use that they are detrimental to the economy, the availability of equipment, and the enjoyment of the game.

They are inferior in every possible way.