They get a one time only amount of cash (not much) and are stuck with a lifetime of recurring costs. I can't see that being a sustainable business model.
Proceed with caution on any "lifetime" deal that is too cheap....
Under the terms/conditions it says it's only a 5 year subscription. Still a good deal but after that it's $500+ and that would be one hell of a recurring fee if you forget to cancel.
There is a huge difference between the services, quality, security, and reliability that different VPN's offer. If you're looking to get a good one you better be careful about paying bargain basement prices. A well established reputable one is a better choice, and it won't be the cheapest.