You are correct to note 'real' costs of the leading labs are not public. It is surely true that the labs are operating at below cost (we are definitely not paying for the full R&D), but it seems unlikely that this fully explains the reduction in inference costs over the last years. We also know from open models like deepseek that the cost per inference token at a fixed performance level is going down very quickly matching the curve of leading labs inference cost decreases. You can even test it yourself on your own pc if you want.
I would add that inference cost decreases is what we should expect, it stands to reason there will be algorithmic improvements in inference, and compute cost is still going down just because of (a somewhat sloped) Moore's law.
Maybe you could also be a bit friendlier and forthcoming in your responses.