Open source models costs are determined only by electricity usage, as anyone can rent a GPU qnd host them Closed source models cost x10 more just because they can A simple example is Claude Opus, which costs ~1/10 if not less in Claude Code that doesn't have that price multiplier

But Kimi seems so big that renting the necessary number of GPUs is a non trivial exercise.

Exactly! Electricity, hosting, and amortized cost of the GPUs would be the baseline costs.

Open source models can be hosted by provider, in particular plenty of educational institutions host open source models. You get to choose whatever provider you trust. For instance I used DeepSeek R1 a fair bit last year but never on deepseek.com or through its API.

* It's cheaper than proprietary models

* Maybe you don't want to have your conversations used for training. The providers listed on OpenRouter mention whether they do that or not.