They get paid for another month, or maybe a few, until the advertiser sees that their ads now cost more than the revenue they bring in, as the fake/purchased clicks don't ever buy the company's products or services. At that point logic dictates that they cancel their ads with Google. Google would have earned that bit of money either way, but now they've lost all the future revenues from that business.
If you dig into almost any AdWords account and make a custom report that includes the "invalid clicks" column, you'll see that they already don't charge advertisers for a very large percentage of ad clicks. I have an "invalid activity" credit in my billing statement just about every month, which is an automatic refund for potentially fraudulent clicks that weren't detected immediately. You don't generally have to ask for the refunds, it's in their best interest to cancel those clicks and keep advertisers' ROI positive so they continue paying in future months.
If you dig into almost any AdWords account and make a custom report that includes the "invalid clicks" column, you'll see that they already don't charge advertisers for a very large percentage of ad clicks. I have an "invalid activity" credit in my billing statement just about every month, which is an automatic refund for potentially fraudulent clicks that weren't detected immediately. You don't generally have to ask for the refunds, it's in their best interest to cancel those clicks and keep advertisers' ROI positive so they continue paying in future months.