Google Maps prevent attack to force multiple requests

Question

Recently Google Maps has updated its prices and it makes me wonder what happen if a malicious user decides to visit a website with a Google Map, open the developer console of the browser and write a loop which makes requests to google maps using the key of the visited website.

I guess Google Maps will see these requests as legitimate because they come from the domain associated with the key, so this requests will count for the billing.

Am I right? How we can prevent this attack?