Ads Manager has such a feature with "Promo thread" ad type. After it expires, the thread won't be deleted but it can be moved automatically to a custom forum which can be hidden and if the user decides to renew it after a while, it can be done more easily.
It is probably custom made. I have made a different add-on where you can allow users to convert their trophy points to cash or something else. So you basically award them points for posts or any other activity that the trophy point system supports and set a conversation rate where they can...
Like any other add-on.
ACP > Add-ons > Install/upgrade from archive
Once installed, set the user group permissions and change the admin settings according to your needs.
You can do that if the ad is not inheriting package settings.