Its really depend on what you include and exclude as "Production...

Its really depend on what you include and exclude as "Production Costs"

For example, for PLS (Sept Qtrly)

3 Unit operating cost (FOB Port Hedland excluding freight and royalties) includes mining, processing, transport, port charges, and
site based general and administration costs and is net of any tantalite by-product credits. It is calculated on an incurred basis
(including accruals), and includes inventory movements, and credits for capitalised deferred mine waste development cost, and it
excludes depreciation of fixed assets and right of use leases, and amortisation of deferred stripping

and

4 Unit operating cost (CIF China) includes the unit operating costs (FOB Port Hedland excluding freight and royalties) plus freight
and royalty costs. Royalty costs include a 5% state government royalty on the FOB selling price, a 1% native title royalty on the
FOB selling price, and a 5% private royalty on the FOB selling price which is only applied to a part of the resource/reserve acquired
following the Altura Lithium Operation acquisition

Then you compare it to IGO (Sept Qtrly)

5 As of 1 July 2023, IGO adopted a revised cash cost reporting methodology as a more appropriate measure of cost performance at Greenbushes.
Cash costs (production) includes mining, processing, crushing and site administration, and utilises production as the unit of measurement (as
opposed to sales). For clarity, inventory adjustments, non-site G&A, offsite and royalty costs are excluded.

This Mkt index didn't bother to read the fine print - probably just took the headline numbers and accepted it.