Silicon is pretty damn abundant, and they're complaining about how expensive it is -- it's the processing that matters, and right now processing cheap, abundant carbon to make defect-free layers of graphene, or uniform mixtures of carbon nanotubes (free of catalyst particles, of identical chiralities, lengths, diameters and tube number) is very hard and expensive.
Personally, I'm super interested in what Twin Creeks Technologies (http://www.twincreekstechnologies.com/solar/ -- no affiliation) is going to do. Their processing technology is completely out of left field and seems like it has huge potential.
I just had a proposal rejected by dept of energy for a composite metal/ceramic ITO replacement :)
But it seems clear that prices for these materials is dropping - and will drop much more in the future, especially with industrial demand. Interesting times!
This graph helps place, what you're talking about, in perspective.