21 cents isn't the true cost but cool nonetheless. He's on the free tier available to new signups for up to a year. For that matter he could have run it on T2.micro and it would still have cost pennies. Still, a neat setup. (Edit: Lambda's free tier isn't time limited, as noted in other comments below)

Lambda requires a lot of boilerplate and configuration to get things setup. Even when you use Serverless/Apex/Gordon, there's quite a bit of configuration to do. I found ClaudiaJS (https://claudiajs.com/) is much quicker to get up and running and it sets up the API gateways for you based on your API signatures.

A 35mb jar deployment has gotta be painful (zip, upload, deploy). It helps to have a local dev and testing setup off the get go. Once you get past all that, working on your codebase can be fun again.