It looks like whoever registered the website theilluminatiball.com made it private. The address listed here is the headquarters of domainsbyproxy.com, and the person's name isn't listed either. It's interesting that it was registered in 2015 though. Perhaps there have been other balls in previous years?
https://www.whois.com/whois/theilluminatiball.com
So it does appear that theilluminatiball.com has been around since 2015. Here's an early archive of it from November 2015. It looks mostly the same except the event it advertises is in 2016. It's got the same contact page and Georgia Guidestones thing and everything. So this has been going on for a few years now. It isn't something new, it's just something nobody noticed. I'm still not 100% convinced it's actually tied to the Rothschilds but obviously there's money going into it so that money has to come from somewhere.
https://web.archive.org/web/20151214174317/http://www.theilluminatiball.com:80/