Costs in the cloud can be unpredictable. I learned this the hard way when I ran an Azure Function in consumption mode (serverless mode) and noticed that it was being used millions of times by an out of control application. As you pay per execution of an Azure Function in consumption mode, that months' cloud bill made my credit card very unhappy.
There are several techniques that you can use to take control over your costs in the cloud and avoid my mistake. You can learn about them in my new Pluralsight course Evaluating and Controlling Cloud Costs: Executive Briefing, which is a short course that you can easily finish in a lunch break.
Let me know what you think about it.