You can attend the main event for free. HOWEVER, to be frank, it is a much better experience to upgrade and pay for the pass. That's the full experience of this summit.
As soon as you upgrade to the paid ticket, you'll receive ongoing access to all replays (what people call "life-time" access).
Once you have paid access, you can slow down, knowing you'll be able to watch the sessions more than once. You can return to the talks that spoke to you the most and watch them in your own time, long after the event is over.
This pass also gives you a series of great bonuses from the experts all around the world.