It’s not just price and speed, the API is very well designed for classification. Going beyond the current structured outputs.

The available API shapes have limited so much over the years. It's really hard to come up with a new one and have it used, so everyone just tries to fit their work into the existing APIs (chat/completions).

Good job to them for putting out something that does seem quite nice to use, and will likely get a bit of wider traction.