Emily Nakashima's session from Monitorama PDX 2023. Advances in monitoring and observability have given so many of us the confidence that we knowing what's happening in every corner of our systems, but for many teams, one system facet remains stubbornly un-observable: cost. This talk will tell the story of how a surprise giant AWS bill sent our growing startup engineering team on a mission to be able to observe our cloud spend with the same clarity and immediacy as performance, reliability, or any other important system characteristic. I’ll walk you the techniques we’ve attempted to observe cost, sharing the pros and cons of each, and I’ll also talk about how we’ve used this data as a basis for re-shaping team practices, building out an internal training and support program that has helped our whole engineering organization get fluent in balancing cost against our other operational and business concerns.