Most AWS cost work goes wrong because it starts with the biggest line item, which is also the riskiest. Order the work by blast radius instead: free networking and storage fixes first, performance envelopes one workload at a time, and commitments last. Includes the commands to find the waste and the cuts that look harmless and are not.
Choosing between Lightsail, EC2 and ECS for a small client workload is not a performance question. It is a question about which constraints you are accepting and how expensive they are to reverse. Profiles of all three with where each wins and loses, the cost levers that actually move the bill, a six-step decision procedure, and the arguments that fall apart on contact with a real project.
"EC2 – Other" is the third largest line on the bill and you run no EC2 instances. That's NAT gateway charges from a pipeline that is entirely Lambda, S3 and Athena. Five levers for cutting the AWS cost of Salesforce data pipelines, in the order worth pulling them.