As a payments processor, Stripe has conversion data. They can route based on ROI with end-to-end A/B testing or online optimization. There's a tricky credit assignment / multi-touch attribution problem to solve for some use cases, too, that could benefit from transfer learning across their customers. Also, the (unstructured) data they collect from OpenRouter users can be used to improve many other dimensions of their business, including fraud detection. Lastly, both businesses look fairly similar in unit economics if you squint hard enough; for example, they both collect a ~3-5% transaction fee from most customers.