If you're a new member you get access to the batcave immediately without 500 posts but for most members there is no additional content yet.
Right now it's just a way to contribute to the running costs of the site and by it you get some perks like custom user title colour but as for now, no additional content yet but it will come, I have some ideas.
The site is costly to run and we haven't had any ads at all for 5+ years, I might have to add some ads for guests or newbies at some point though to ensure the quality and uptime, for example we have a dual dedicated server setup just for the main site and more servers for extra services.