Ask HN: Did pricing calculators work out for you?

I'm budgeting for a new project and it struck me that I've no idea how much faith I should really put into a cloud pricing calculator. (e.g. AWS' https://calculator.s3.amazonaws.com/index.html)

It's complicated enough that I could easily miss a foot-gun, and clearly a sales tool: there's plenty of wiggle room built in to how prices are calculated in the end.

Have you ever compared your actuals to the estimates you started with? Were they accurate? Miles off? If not how then did you budget for cloud costs? Or did you skip that and just see what happened?

Same question goes for the other clouds/providers etc.

Thanks for your time!