The amount of power packed away in this little uncommon should not be underestimated, particularly in kindred-based Commander decks
Ruby/Amethyst might feel too simple for advanced players, and Steel/Emerald could feel confusing for beginners.
As you can see, the number of cards one can use to fill the graveyard is a very short list
Elspeth does the job of a big game ending threat very well, whilst also retaining some nice planeswalker-like utility
That's all down to personal taste, of course - and as the price reflects, this isn't one of the most desirable promo cards out there
It's also only found on red, white, or blue creatures as it was originally a keyword associated with the Jeskai Way faction in Khans of Takir