Answer:
When it comes to me, you go on red and stop on green. What am I?
I must be broken before you can use me. What am I?
You throw me away, I find my way back. Traditionally, I'm wooden with an arch in my back. What am I?
Fatherless and motherless. I was born without sin. Roared when I came into the world, but I never spoke again. What am I?
What gets bigger the more you take away?
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.