www.wysiwygwebbuilder.com

I would like to know if, for me, who already has the wysiwyg web builder 20, how much would the extensions cost, and also if the access is for new extensions and if the validity is forever?

You can purchase individual extensions via the website.
https://www.wysiwygwebbuilder.com/extensions.html

Or bundles:
https://www.wysiwygwebbuilder.com/promotions.html

The price does not include new extensions, because it takes a lot of work to create these extensions.