Austere Command is an extremely powerful board-wipe in the Commander format. Because of this, it was included in one of the Commander 2011 pre-constructed decks. But outside of its original Lorwyn printing, that was the only other time that it was released. Because of its popularity in the Commander format, both printings run more than $7 a copy.
Why is it so good in Commander? It gives you options. 6 mana seems like a lot to pay for a boardwipe, but you get to choose 2 of 4 options. You can destroy all artifacts, all enchantments, creatures with converted mana cost 3 or less, or creatures with converted mana cost 4 or more. Considering all of these options, it can be extremely one-sided depending on who's playing it.
While players are definitely happy that Cryptic Command was reprinted, it turned out that Incendiary Command and Austere Command would not be reprinted at all. Primal Command, however, would be reprinted in the Duel Decks: Zendikar vs Eldrazi. It was hoped that a new supply of non-foil and foil versions would make Austere Command much more affordable. Cryptic Command saw a price dip even due to everyone wanting four copies of it. With Austere Command you'll probably ever only need one, but since no new copies have entered the market, its price is only going to continue to rise for some time.