Inference costs aren't a problem, selling inference is almost certainly profitable. The problem is that its (probably) not profitable enough to cover the training and other R&D costs.

You did not parse that article properly. It regurgitates only what everyone else keeps saying: when you conflate R&D costs with operating costs, then you can say these companies are 'unprofitable'. I'd propose with a proper GAAP accounting they are profitable right now; by proper I mean that you amortize out the costs of R&D against the useful life of the models as best you can.

I am not aware of any frontier inference disclosures that put margins at less than 60%. Inference is profitable across the industry, full stop.

Historically R&D has been profitable for the frontier labs -- this is obscured because the emphasis on scaling the last five years has meant they just keep 10xing their R&D compute budget. But for each cycle of R&D, the results have returned more in inference margin than they cost in training compute. This is one major reason we keep seeing more spend on R&D - so far it has paid, in the form of helping a number of companies hit > $1bn in annual revenue faster than almost any companies in history have done so.

All that said, be cautious shorting these stocks when they go public.

Do you mean as part of going public they need to make public how much they spend on inference versus how much they make?