Ive dealt with this error at AWS. It’s a unit error. In my case we _meant_ to charge like 5¢/GB, but missed the unit (GB), and then the billing system defaults to bytes. 5¢ per Byte of data transferred meant some customers were seeing MM bills within hours. Got paged by support around 2am, had it fixed and amendments issues by 3-4am, apology emails shortly after. Services emit metering values that arent directly tied to prices. Every SKU/line item is defined in a “pricing plan”, with a unit type, regions, and price per unit. The metering records are joined to a pricing plan based on account id, region, sku, etc. mess up the unit type in the pricing plan and the metering data conversion doesnt work, and you get crazy bills. There will have been tests, but there will have been missing end-to-end tests. Test 1 will verify that the new system/product emits billing entries in some expected way ("We did 100 bytes of operations and we see we called the billing system for 100 bytes of stuff, yay, test pass").…