Didn't Say Please

The extra mana over Counterspell buys a rider that does nothing to whether the spell resolves, and that is the honest way to read it: this is Cancel with a mill clause bolted on. The counter is the whole transaction; the three cards off the opponent's library are fine print. Against most decks the mill is decorative, a small ding to a resource almost nobody is protecting, and against the wrong deck it is a liability. The design leans on a specific asymmetry in blue's toolkit, where feeding an opponent's graveyard flips from harmless to counterproductive depending on who is across the table. Point this at a deck built around graveyard resources (delve payoffs, flashback, reanimation) or one actively trying to empty its own library, and the rider hands over exactly what that deck wanted, accelerating its plan while you were trying to stop it. That is the tax the caster accepts for a permission spell whose second line can only ever hurt or do nothing, never help, unless you are the one racing the opponent's deck to zero. Where the mill earns its mana is in a deck already committed to that plan, one grinding the library down as a wincon, where every permission spell doubles as a chip off the clock. Absent that build, the third mana pays for a slightly worse Counterspell and a coin flip on whether the mill was neutral or a gift.