Far Future. Almost every household has a 'fabber'. You put raw materials in it (can be almost anything) and it does what you program it to do. It transmutes the raw materials into what is needed. Then it basically 3-D-prints it. It only works if you have enough and the right quality of input material for the end product.
I am looking for a logical, chemically sound (does not have to be hard science) system how valuable the input materials are.
The first property that came to my mind was density. Would the most dense materials be the best to fuel the transmutation? Would Uranium be a better raw material than wood?
The materials are not constructed from the ground up, they are changed via (complete layman here) chemical or physical reactions. You know (I don't) changing number of electrons etc.
EDIT: Thanks to Burki I was able to decide that the 'fabber' is a chemical (dis)-assembler. This means that the transmution is limited to chemical changes.
Energy is cheap, but not unlimited. Obvious valuable items are the blueprint for advanced items, of course. But raw materials? How can they be ranked and classified?