They could easily cut off public access to those resources while charging you storage fees. Obviously with any kind of ceiling there are certain details that need to be ironed out (i.e. most people wouldn't want configuration information or data to be lost, but they likely would want VPS to be taken offline and other services to be suspended).
Ultimately for most startups, small businesses, and individual developers being able to say "My AWS bill cannot exceed $1000, period" is a powerful tool. Right now if a billing alert fires at 1am, you may not see it until 9am and by then you're already in huge trouble.
SNS topics and lambda jobs. Just use the API to add a firewall rule to block traffic when it gets a billing SNS alert. Should be pretty simple to get working.
That's still a very striking omission of a feature.
Lambda isn't available in all zones, and not everyone has the time/ability/knowledge to set up such a thing. I'm sure I could do it, but only if I were to spend a few hours researching it, and probably a few nights working on such a solution. I'd also have to trust that I didn't mess it up -- I'd hate to have a bunch of traffic and NOT properly prevent the traffic.
This is the kind of thing that Amazon surely could provide easily if they wanted to.
It's like if your phone company didn't give you an option to limit your spending (prepaid), but said that you could use their arcane API to tell them each month to start/stop service. That's great, but not really very nice to customers.
The monthly budget cap should be allocated to existing storage first. This covers the existing data for the next month. If there is any free limit left, it could be used for new data writes + 1 month of storage, and/or running services. Once the limit is reached, then writes are blocked and services stopped.
The only situation where you would need to delete data is if you want to set a new monthly budget that is lower than your existing monthly storage-only bill - but the UI could just disallow this.
They could easily cut off public access to those resources while charging you storage fees. Obviously with any kind of ceiling there are certain details that need to be ironed out (i.e. most people wouldn't want configuration information or data to be lost, but they likely would want VPS to be taken offline and other services to be suspended).
Ultimately for most startups, small businesses, and individual developers being able to say "My AWS bill cannot exceed $1000, period" is a powerful tool. Right now if a billing alert fires at 1am, you may not see it until 9am and by then you're already in huge trouble.