Cloudwatch costs have been the ones my coworkers complain about. The one that got me was sagemaker -- the console had a bug where if you went to a region without endpoints, it would pop up a tutorial screen and the tutorial screen would "stick," hiding endpoints in other regions. Which led to hanging endpoints, which were covered by free tier for a few days before costs exploded. We had alerts active, but they alerted when we span up the resources, which was expected, and didn't make it obvious that paging through all the regions ensuring there were no running resources (itself painful) and watching daily costs for a few days was insufficient to ensure that we weren't going to have a $700 bill at the end of the month (or maybe $1400 -- I forget if $700 was the half refunded cost).

When I shared this anecdote at Re:Invent, the sentiment at the table was "lol that's cute, here's my story with an order of magnitude higher price tag." There were 5 or 6 of us, and my story was the smallest surprise cost except for one other person who was even greener than I was.

> Can you provide an example of a service that the AWS calculator doesn't compute the correct price for?

Can you tell me how I should have used AWS calculator to prevent my surprise charge? You can't, because AWS calculator assumes you know exactly what you're asking for, and the problem with opaque pricing structures is that you sometimes don't.

Other clouds tend to be much more upfront about "this will cost X," "this is costing X," "you're out of free tier," etc.