Because nanites are so small, they require little in the way of raw materials, just a few molecules here and there.
Clearly, what nanites will do inside our bodies in the future is almost limitless and will change medicine forever.
In the future, we will paint surfaces with substances full of nanites that will absorb sunlight and turn it into electricity, transforming any object we paint into a clean energy creator.
Or how about nanites that process each piece of trash in our garbage and turn it into something useful?
Or nanites that clean up any toxic chemicals they find and turn them into harmless agents?
I branched off into this discussion of robots and nanites to give an idea of the kinds of massive gains in efficiency with declining costs.