Yes, check this: http://www.italian-online-lessons.com/quanto-costa/
The singular form - quanto (masculine) or quanta (feminine) - usually translates as "how much"
The plural - quanti or quante - is usually used for "how many"
Also "How many is it?" isn't really good English - the more common way to say that is "How many are there?" (as you can see the verb is plural here in the English version - as it should be in the Italian equivalent: "Quanti sono?")
Hope that helps
In English we would say "Why does it matter if I say?" That is just to help you with your English.. Now, to answer your question, in a question the verb usually comes before the subject: "how much is it?" instead of "how much it is?" The answer,since it is not a question, would be "It is fifteen", or "it is a lot" or "it is not enough."