Ask HN: How do you manage cloud infrastructure and services costs?

I'm curious how people here estimate and evaluate the costs of IaaS/PaaS (e.g. AWS, Azure, Heroku) and third-party cloud services (e.g. Algolia, Loggly, Twilio, etc).

Does cost ever influence technical decisions around languages and stacks?

Do cloud infrastructure/services costs ever influence product decisions (e.g. not moving forward with a feature because the computing costs would lead to terrible unit economics)?

Obviously, exact costs for infrastructure can be hard to predict. How precise do you try to be before making a decision? What process or tools do you use?