comparison economic figures FYI HEG ATC, page-6

Because the margins are so large the CAPEX, as an up front cost, has a proportionately much bigger impact on returns. You can see this with the much higher returns forecast by FYI and HEG.

 OPEX is mainly made up of labour, gas,  electricity and transportation (shipping). I think FYI and HEG plan to build and operate in Australia. Cost per unit will therefore be much higher for HEG and FYI but they don't have to ship ore to Malaysia for processing costing between AUD1,500 to AUD 2,000 per tonne of product and their bigger plants should generate greater efficiencies  hence the broadly similar OPEX per tonne of product.

Having said this looking at things objectively FYI and HEG have only completed to PFS level and not had to go through  rigorous German due diligence. Nevertheless I would be very surprised if the FYI and HEG CAPEX blow out as much as Altechs.