I am also convinced that this attack is nowhere near is strong as Cutpurse. Cutpurse is painful because as long as you have Copper in hand, that guarantees -$1 on your turn. This card gives the "defender" a lot of flexibility, and most importantly, generally benefits him if played early. Early you'll be replacing Estate with Copper, which, barring TfB and Baron, is a good thing. Even when you don't have an Estate in hand to trash, it's not that bad to take in a Copper early on, sometimes that can be helpful for hitting $5 more easily. Later on it becomes either a junking attack or a Cutpurse, whichever is less painful for the person taking the attack. Cutpurse is pretty good early, but it's not so great mid- and late-game, and it gives +$2, which is better than +$1 or +1 card. Witch and Torturer are priced the same, but Torturer gives another card, which is a pretty big bonus, in exchange for giving an option to discard two. Even if this had the same discarding effect as Cutpurse, giving it both an alternative attack option and a weaker vanilla effect should be plenty to make it fair at $2.
Also, consider that the two main differences between a card costing $2 and a card costing $3 are that (i) it's easier to pick up lots of $2's and (ii) you can open with a $2 and a $5. This is terminal, so I don't think (i) is a concern, and I don't think there's anything crazy you could do by opening this/$5. I don't really see why pricing this at $2 would be a problem.