The mechanism is the product itself: Heidi's brain holds full context on her own codebase, so the expensive part of AI development, re-extracting context on every request, disappears. Writing code is cheap; rediscovering what the code means is what burns tokens. With the Cortex holding the meaning, a full working feature costs two to three dollars.
The autonomy is real and bounded. One night she hit her database limit, provisioned a new instance, and migrated herself by morning, logged, with receipts, inside limits Falk set. That engine, the one that built her, is what every customer install runs on.