Although I'm unsure if this is the Japanese booster box's lowest ever price (my price-matching software is failing me and not accounting for postage, etc), that's still a very unusual discount as well
This action (known as a 'mulligan' in other TCGs like Magic: The Gathering) is generally taken when a player's opening hand doesn't have enough ink or too many high-cost cards
Add to that the coven ability to also play creatures, and we have a strong 3-mana human in Augur of Autumn
As can be seen by cards like Krosan Grip or Return to Dust, one particular sword is always being destroyed in some manner by the spell being cast
Combat : Apply damage, put dead creatures in the graveyard, and subtract HP
Why its a contender: This creature is the modern embodiment of overwhelming efficiency, providing mana, card advantage, and a must-answer threat all on turn one