The Eternal Flame was not a blazing flame, but the name of an elemental crystal.
Things in the game differed greatly from those in the real world. Items that were everywhere in the game became precious in reality, while things commonplace in reality were valuable in the game. These differing perspectives created enormous cultural differences.
The Eternal Flame belonged to a whole series, all members of the Eternal Family. The family also included eternal water, eternal air, eternal earth, eternal life, and eternal shadow.
There were many ways to obtain an Eternal Flame in the game, so it could hardly be considered anything special. Anyone determined to collect them could farm piles of them without much difficulty. In the real world, however, its value had increased a hundredfold. It was an elemental material even more precious than titansteel.
The Eternal Flame was not a naturally occurring elemental material. It was created by fusing ten Fire Crystals, so anyone wishing to make one first had to find ten of those crystals. Fire Crystals were extremely difficult to obtain. They sometimes occurred alongside titansteel, giving miners a chance of finding them while excavating the metal. Another option was to hunt powerful Fire Elementals, such as Ragnaros, who occupied Blackrock Spire. Killing him would guarantee precious elemental crystals.
On the surface, there seemed to be plenty of ways to obtain Fire Crystals, making the creation of an Eternal Flame look easy. That was merely an illusion. The final fusion required ten Fire Crystals, which severely limited the chances of an Eternal Flame being produced. Even if someone found Fire Crystals while mining titansteel, they could not fuse them without a full set of ten. Moreover, the fusion required a grandmaster; otherwise, the risk of failure was high.
In short, all these factors meant