The Sentry team used Metrics to track custom data points and identify the issue of high ingestion costs, specifically with the `save_event_transaction` task, which was costing around $160k per year. They set up Metrics to visualize computation time for this task and found that 51% of the time was spent on setting the cache, resulting in significant cost savings. The team made several impactful changes, including optimizing caching, improving traffic distribution, unblocking third-party tools, and moving away from Twemproxy to Mcrouter, which resulted in reduced costs overall. Through a collaborative effort, the Sentry team achieved substantial time and money savings using Metrics.