Here is the challenge with that solution. Extended permissions work by adding conditions to database queries issued by WordPress, so that the post/page which the user doesn’t have permission to will be excluded from the result. Basically WordPress will act such a way that the post/page doesn’t exist within the site, hence the 404.
The solution you are asking is possible by allowing WordPress to fetch the page, but redirect or replace the content when user access the page. The replace content functionality is already there in this plugin and is called Content Shortcodes.
For your purpose I recommend using Content Shortcodes, so that paid members will see the actual content, non-paid members will see a message and guest users will see a login form.
Available only for paid members