I see no evidence anywhere that "inference is cheap". To my knowledge this is a myth being spread to pretend ChatGPT or Claude will one day make any economic sense.

DeepSeek likely operates at a loss. How big the loss is anyone's guess.

Meanwhile I am happy using their model. It is really good, to a point I forget I am not using Codex or Claude.

DeepSeek is very likely selling tokens at a loss. There're many cloud providers that provide you with DeepSeek V4 Pro via API, and those services at least twice as expensive as DeepSeek itself.