I was also about to ask. How much?
What would this example cost if someone decided to test it themselves?
We hit the one million connections total probably between 10-20 times over the course of a couple of days, and probably spent at least another 20-30 runs working our way up to it, testing various things along the way. Keep in mind, these were all very short-lived test runs, lasting maybe up to 8 minutes at the most.
Our total bill for Lambda in the month of October came out to just over 50USD.