Answer:
Of these things - I have two. One for me - and one for you. And when you ask about the price I simply smile and nod twice.
I run up and down the stairs without moving
The more you add the less it weighs. What is it?
I am three simple words everyone wants to hear. Three simple words such simple words and yet...life changing...
I am one small little piece of paper yet sometimes hold lots of value. I am all you need to get in to big events but will cost you. I am an important part of travel. And if lost you're not coming.
I break away from my pack. I create holes in my victims. I can travel for miles and then disappear. I am part of a dying breed. What am I?