This is not a "Serverless" problem; this is a mistake a developer made that used a pay-per-use system. If I write code that launches EC2 instances and I accidentally set it to launch an instance every second instead of minute because I divided wrong, that's my fault.
Its not a "problem" with server/serverless of course, but no-scaling-by-default vs unlimited-scaling-by-default (which is imo the better way to split the server/serverless topic), one is going to cost more when things get thrown for a loop