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
We had a database growing by around 200GB of relevant data per month. While I'm not a fan of Oracle having worked there long ago, that database was unbelievably fast. They moved to MySQL years later and it required a much much bigger tin after being heavily optimized.
Outbound traffic from US/Europe is $0.0085 USD per GB. That's roughly an order of magnitude cheaper. Also, 10 TB free will be enough for many small use cases. The billing based on source instead of destination also makes the cost a bit more predictable.
That's just list price, of course, and it's still well above e.g. Hetzner, but it's a reasonable price.
Cloud native can go to either extreme cost wise, and it's very dependent on good engineering (which, unfortunately, is the exception not the norm).
In the end of the day this is THE cheapest cloud available if you just want few VMs with database and under 10TB of traffic monthly.
Personal opinion: it is much easier to manage than AWS.