How mUch does it cost ? The auxiliary verb /to do/ is necessary in almost all of the interrogative sentences, with the exception of the ones where the verb is /to be/. does : verbal voice from /to do/; third singular person. A grammar book does seem to be needed! (here /does/ is used for emphasis, and is not needed)

Because - it.

does is part of the verb phrase. It is not true that does is needed. It could be replaced. But something is needed to hold the idea of "being". The Idea of being is like saying, "What is the state of being when it comes to the price?" So how else could it be said? How much will it cost? How much should it cost? How much could it cost? How much must it cost? How much might it cost? How much may it cost? How much is the cost? How much can it cost? Some of these are closer to does in meaning, and others change it some. But the point is, we are not repaving does as much as we are doing the job that does has- which is naming the state of being. That is what must be done.

"...it does." "...does it?"