[hylaride]

This highly depends on workload. We migrated a service that generates terrabytes of content to send to customers each day. We moved the content generation from J2EE to java lambas and our costs went from $6K/month (on savings plans, evemn) of ec2 to ~$400/month in lambda, sqs, and elasticache/redis costs and the work was done in 1/8th the time. Mind you, our content is highly bursty where we need to be able to generate the content within seconds seconds of initiation.

Serverless also means a lot of things. We also serve static content from an S3 bucket and cloudfront. Nothing else to manage once its setup.

The flip side of serverless is you really do need to think of state yourself. The J2EE code was rock solid in reliability, including recovering from almost every kind of issue you can imagine over a decade (database, connectivity, software crashes).