I haven’t tried seedbox, but Usenet is very cheap and you can consider it similar to having private trackers I suppose. You will find many releases on Usenet that you will only find in private trackers. Also you don’t need seeders, so as long as the file wasn’t removed by DCMA you can download it.
It is a deal, it is only for a limited time. They do deals like this from time to time. The deal lasts for 12 months then goes back to regular price.