I can't see any features listed that enable me to control costs to prevent surprise bills. If a site got submitted to HN and hugged to not-to-death-because-it-autoscales then I'd wake up to a bunch of alerts and massive outbound bandwidth bill. I don't want that. I want something that stops that happening.
If the App Platform doesn't have that feature, and it isn't planned, that's OK but I'd argue that isn't really preventing a surprise bill as the marketing site claims. A warning isn't quite the same as prevention.
This is exactly the sort of thing I'm talking about, but for money rather than computing resources or bandwidth. I'd like a feature that where the requirement is effectively "Fall back to a serving sorry-I'm-poor.html instead of the app if the total monthly bill has exceeded $xxx". For a side project I'm more interested in not paying an unexpected bill than getting traffic.
I think for most companies, it's better to set the expectation that the service costs money, bursts will cost more money, and then forgive outlier charges once or twice. It's tremendously difficult to compete against the AWS's of the world, putting work into features specifically to minimize how much people spend seems like a good way to fail a company.
If for some convoluted reason this is wrong, then you guys really need to reconsider how you're presenting your prices and to lay out exactly what those convoluted reasons are, because Fly's pricing page certainly tells people that trying to match DigitalOcean's $5 plan is going to cost 10x on Fly.