Faction discount

The faction discount is a percentage discount when buying items based on reputation with the faction of a vendor.

As of Patch 2.3, all vendors with an associated faction now give discounts at all levels above.
 * : 5% discount
 * : 10% discount
 * : 15% discount
 * : 20% discount

This includes the riding skill below expert and mounts.

In 3.2 the faction discount has been expanded to apply to flying mounts, through Thrallmar/Honor Hold reputations.

As of World of Warcraft: Cataclysm, goblins always receive the best available discount, regardless of reputation. This means that you get a 20% discount even when at neutral reputation with a faction, despite normally only being applied at exalted reputation.

Faction discount