The Northrend Flying Mount skill is no longer free through the Sholazar Basin questline. It now costs a whooping 1,000 gold.
Tigole: Yes, it will be 1000g when it goes live. It was originally part of a quest line but we found that it wasn’t intuitive where to get it. We also tuned the cost around the amount of gold you will have accrued by level 77. Unless you’re spending excessive money on the AH as you level up, you will have more than enough gold to afford the cost.—Source