[curiouscat]

Conducting a costing feasibility study for a process got me thinking:

What are the cheapest reasonably pure, hydrocarbon feedstocks, say on a per-kg basis? Bulk prices.

Let's exclude mixtures (e.g. diesel, fusel oil, natural gas etc.). Let's assume C and H are mandatory while all other elements are optional.

Further, does the presence of certain elements (Cl? Br?) or structural entities (aromatic rings? heterocyclics? chain length? ) etc. make a feedstock any more expensive; are there any such heuristics?