[amykhar]

It could be trivial to do it though. Depending on how sophisticated you need the interface.

If you set up a subscription that put the paid members in a new usergroup, you could have a plugin for showthread that checks the threadid and the usergroup and kicks the user to an error screen if they haven't paid.

Heck, you could even use template conditionals to blank out the content if they haven't paid.

It becomes more complicated if you want checkboxes and such or the ability for others to set up paid threads.