If you can make a mach 12 missile for less than 1 mil, yes, there are other option first.
Just in case you don't understand why I said that. If a missile cost that little, it's either ship or air launch, to which the first line of defence is to expel that threat beyond their engagement distant. The more cost effective way to handle that threat is to send up aircraft to engage the air/naval platform that lunch the missile. You don't expect you can just go and sit in range inside your enemy and launch missile all day undisputed. You aren't talking about Russia fighting Ukraine, you are talking about the US.
If the object gets closed enough and launch that missile, then you can talk about missile defence system. But there are several layer before that, Detection-Suppression-Interception is the basic of Air Defence Doctrine, as I said, you don't just go launch missile everytime....
That is Iranian ballistic missiles launched from ground.
I think you need to do a little more reasearch about this area.