The fact that you can regain cards (unless you have lots of really expensive cards in hand AND still want to use it, which is uncommon enough for it not to matter) makes the "exactly" being really similar to "up to". I think this is strong, but is probably not a lot stronger than just "Trash 3 cards from hand.". I mean, I think the gaining from trash has close to neglible effect in 99% of the games, and trashing 3 cards from hand is good. However, with Chapel there, it seems a bit redundant.