That’s completely misunderstanding why the cost increased. 95% pure carbon is worth next to nothing per pound. 99.99+% carbon is really difficult to manufacture. If battery manufacturers thought they could do it for less they would manufacture things in house, but purification is both difficult and expensive.

If it is so easy[0] go start a company and undercut them. Raw materials are commodities, if you can make battery grade materials for less - in bulk - someone will buy them (or buy you out to protect their monopoly).

[0]its not. Batteries have exacting purity and qc requirements that meeting and maintaining is neither trivial nor cheap to do well even at small scale.

What sort of processing are they doing? It seems like processing those materials to be pure and consistent could be pricey. Maybe not a perfect comparison, but raw silicon costs $1-2 per kg, but can cost several hundred per kg once processed into wafers.

Are you sure it isn’t, at least partly, due to intrinsic costs of turning raw materials into usable materials?

Silicon as a raw material is dirt cheap, too, but removing impurities so that it can be used makes it a lot more expensive.