If you get it right, great. If you get it wrong then you end up doing billions of operations by mistake, which could cost a huge amount. That's what happened to the author of the article.
But really the first lesson you should learn in any cloud setup is Billing Alarms
Alarms only tell you that something is going wrong. They don't stop it. If your mistake is costing $1000/minute and you're an hour away from a computer you have a very expensive problem.
This is HN, many of us are solo founders with no coworkers or employees. Also how could a "friend" pull the plug? If it was a physical server running in your house maybe, otherwise you can't really give them access to your AWS account with all your private clients data in there.
As for having a non-employee pull the plug, set up an IAM user with permission to access the test instance
Agile. Bringing you bankruptcy at the speed of cloud.
And why would you start a test if you won't be there to see the results of the test? Seems more sensible to either leave after you've run the test or wait to do so until you get back.
If you don't buy one coffee, or put a 20 dollar note in a book one month. Then you're fine. And if you have to use EC2, just use a t2.micro or a raspberry pi on your desk.
But really the first lesson you should learn in any cloud setup is Billing Alarms :)
If you're doing ML or CV work then it's probably cheaper to build on the desktop and port to cloud once you understand what the workloads are.