Your right that all other costs are critical to measuring the profitability of the business but for such a young industry that’s the unknown. Does training get cheaper do we hit a theoretical limit on training. Are there further optimizations to be had.
You don’t have large capex in an industrial and then in year one argue that the business is doomed when your selling the product above the marginal cost but you have not recouped costs yet that have been capitalized.
• Inference used for training? Modern training pipelines aren't just gradient descent, there's a ton of inference used in them too.
• Gradient descent itself?
• The CPUs and disks storing and managing the datasets?
• The web servers?
• The people paid to swap out failed components at the dc?
Let's say you try and define it to mean the same as unit economics - what does it cost you to add an additional customer vs what they bring in. There's still no way to do this calculation. It's like trying to compute the unit economics of a software company. Sure, if you ignore all the R&D costs of building the software in the first place and all the R&D costs of staying competitive with new versions, then the unit economics look amazing, but there's still plenty of loss-making software startups in the world.
Unit economics are a useful heuristic for businesses where there aren't any meaningful base costs required to stay in the game because they let you think about setup costs separately. Manufacturing toys, private education, farming... lots of businesses where your costs are totally dominated by unit economics. AI isn't like that.
- Amortized training costs.
- SG&A.
- Capex depreciation.
All the above impact profitability over various time horizons and have to rolled into present and projected P&L and cash flow analysis.
In part due to base model reuse and all the tricks like distillation. But mainly, due to how much inference the big providers happen to sell.
So, not the massive economic loss you'd need to push models away from being profitable. Capex and R&D take the cake there.