1) Google Chrome doesn't always explicitly ask for a CCV. If it does, the browser dialog opens.

2) It actually charges $1 per CCV check to verify the credit card.

3) If the CCV check is successful, it does the autofill on the form. However, you still have to enter the CCV in the form manually most of the time.

4) The $1 charge is immediately canceled and thus doesn't affect your account balance.

For reference, here's a screenshot of how my bank receives such a charge: http://imgur.com/qwdM9Jx.png

To be clear, this is not from any Google purchase. That's what happens if I use my CC in Chrome on any site.

It also has to be noted that this implementation is pretty bad. On pre-paid CC (i.e. your CC payments are directly tied to your bank account - there is no CC bill), this will negatively impact your spending balance:

Account balance: All your money.

Spending balance: (account balance) - (pending charges)

Some banks refuse to apply the charge cancellation sent by Google and keep the pending charge active for some fixed amount of time (e.g. 90 days).

Assuming that's correct, it really wouldn't take up much memory or computing power to create a lookup table for every credit card number with hash x.