Answer:
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.
Sometimes black, sometimes white, I have veins but no blood
I have a face, yet no senses. But I don't really care, because time is of the essence.
A hole leading in, a hole leading out, we connect to a cavern that is slimy all throughout. What are we?
I never was but always will be. No one ever saw me but everyone knows I exist. I give people the motivation to better themselves every day. What am I?
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.