Very simple question, but the premium pricing page does not have this info on it, if the price is yearly or monthly???

Hello

Thank you for your interest in Nicepage!

Fortunately, the subscription price is annual. You don't have to pay monthly.

Unfortunately, we do not sell domain names. Please check for a third-party company that is registering domain names.

Here's the documentation on how to assign a custom domain name.
https://nicepage.com/doc/1293/assign-a-domain

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Sincerely,
George.
Nicepage Support Team

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The price is annual.
There are differences between the subscription (which needs to be paid annually to keep using it), and license (where you can continue using the final version before updates expire indefinitely). Web app/hosting stops without an active license.

Nicepage doesn't sell domains. You would need to do that with a registrar.