Alleria Windrunner's Price Changed Back To The Original Cost & Now Available For Gold
Blizzard just announced that the price discount for Alleria Windrunner wasn't intentional, hence they're updating the cost back to the original price point + they're making her available for purchase for gold.
Quote from Blizzard
The Alleria Windrunner Hero Set was added to the in-game and web shops yesterday with incorrect pricing and purchasing options. Today, we’ll be updating the Hero Set to the correct price of $9.99 US and also making it available for purchase for 1500 Gold. It may take some time for the pricing to update across all regions and platforms.