I’m using Memberful.com for a membership manager/payment gateway for my site. Hack idea may be to:
Let someone sign-up with Memberful for $X; grant them ability to PM only Admin
Redirect them to a page that asks them to send an admin a PM using the link below
Re-post the paid post as its own category manually as admin
Once you have enough sales, pay for some custom magic to manual reposting
You can use this link: https://meta.discourse.org/new-message?username=Joshua_Kogan&title=My%20Paid%20Message%20-%20PUT%20YOUR%20NAME%20HERE%20&body=Hey%20Joshua,%20here%27s%20my%20post