Festivus What they choose to do is up to them, and whether it will satisfy anyone is an open question. But you continue to say they can't really do anything, when it is obvious they have a wide range of possible responses. One of those options is the one you menioned - vaguely apologetic post, no other changes, and hope it goes away. Let upset players stew, and less upset ones forget about it.
They clearly have the power in the game environment they created to reverse charges, roll back progress, and take back the crowns. That might be a difficult option, it might get them sued (many of us consider that doubtful for these amounts, but possible) and it might irritate more people than it helps. But technically, they have full control over the game world and could definitely make it happen.
And they could do nothing about those who got the sale, but still make a gesture to acknowledge frustration and help people feel a little better about them. Say 2500 crowns for every player who has made a purchase in the last two months, but not at the time of the sale, with an apology in the inbox for the mistake. Or across the board, if targeting is too difficult - crowns and apologies cost them nothing, and might earn back some of the good will they have lost.
I don't think their current path of silence is a good choice. Not very hopeful that they will make a better one, but for the good of the game I hope they find a better option than a generic "we are looking into it" that sits out there until people move on.