Gross margins and cost of revenue are well defined accounting terms that apply to any type of business.

> Does it include:

> Inference used for training? Modern training pipelines aren't just gradient descent, there's a ton of inference used in them too.

No because this is training and not inference. Just like how R&D costs for a drug aren't part of COGS either.

> Gradient descent itself?

No

> The CPUs and disks storing and managing the datasets?

Yes

> The web servers?

Yes

> The people paid to swap out failed components at the dc?

Yes to the extent they are swapping for inference and not training. If the same employees do both then the accountants will estimate what percent of their time is dedicated to each and adjust their cost accordingly.