Also I don't know if I'm missing something, but I just set up a small test site with a small amount of user traffic (<1k requests in total).

I totally can't tell how much this could cost me; I'm pretty sure I'm still under the free quota limit, but I can't see how far I'm into it. I see that there are requests being logged in the API metrics, but the billings pages show 0 usage across all the same metrics.