I still want to work this out, because I like the idea of a trasher that must trash itself to be played. But as you pointed out One Armed Man, that means you're guaranteed $5 per hand. So it should itself probably cost more than that. Like a lot. Like $7. That means that in order to buy it at all, you have to have a deck that doesn't have a lot of junk in it, and then you wouldn't want to play it or buy it.
If it cost $5 then you might want it, and you might want to pay for it, but you'd be very selective about when you played it because you'd want all your junk in one hand because buying this card multiple times would absolutely be a waste of time and money and your opponent would have all 8 provinces before you had any kind of economy.
At $3 you can buy two of them at open, and that would be insanity. Like you said, way too strong and I don't even think swingy is the right word. It's just too strong. At $4 we finally have a situation where you open with it (I was unaware of the award winning Barge card, so for now I will call this card unnamed) and a silver or equivalent, and it only guarantees you one turn at $5 which many openers do, and it only trashes (effectively) four cards. Like Chapel
The reaction part I still like, because if you're buying this for the action then it hopefully finds a curse from that Witch to trash, and if you're buying it for the reaction it only guarantees you a five card hand one of which is this card, which you don't want to play if you want to keep it as a reaction.