Though reCAPTCHA is often touted as a free Google service, it is actually only free for accounts that generate fewer than one million API calls per month. If you are a heavier reCAPTCHA user, Google charges a fee. If your account generates more than 1,000 calls per second, or one million cars per month, you must sign up for a reCAPTCHA enterprise account.
For example, for up to ten million calls per month, Google charges $1 per 1,000 calls. And if you get more than ten million calls per month, custom fees apply. But if your website is smaller, yes, reCAPTCHA is a free service.