1. You're valuable enough of a marketing point that they're willing to give you insane discounts to reel you in (see Zoom)

2. You're locked in enough on other Oracle technologies and they've raised your license fees but coincidentally it comes with a big bundle discount if you also use Oracle cloud, or maybe you just failed an audit and Oracle said the problem will go away if you buy some cloud services.

3. For really small scale (like some dude on r/selfhosted scale, not even startup scale), they offer a free tier that doesn't have a time limit