If you switch to the lifetime billing option during your free trial, you will be billed $699.99 when your trial ends. If you switch during the first 30 days after a charge for a yearly subscription, you will only pay the difference, $580.11. At any other time, or if you’re switching from a monthly subscription, you will pay the full $699.99. No full or partial refunds will be granted for prior payments.
From the current Pricing page.