OpenRouter doesn't do sales, they charge a premium, which is a flat 5.5% taken out of your credits. If you see something cheap on OpenRouter, it's because that one provider lowered its price. (Actually, correction, they will take 0.5% off their fee if you allow them to train your content)

Here are all the providers giving discounts: https://openrouter.ai/collections/discounted-models

Another thing some people don't notice is flex pricing, which is way lower than default pricing, for slightly worse latency and reliability. Depends on the provider and model