People are incredibly fickle; moods and motivations seem to ebb and flow and there's no way to predict whether people will buy tickets even when they look you in the eye and swear that they will. That's because we've been trained from birth to tell people what they want to hear.
Our first conference was sold out and highly-lauded, with GOAT being thrown around. So we did a second one that aimed even higher and while we still managed to break even without sponsors - assuming we donate our time as organizers - we actually only sold about 60-70% of the available tickets.
I remember asking a guy who had said that our first conference had changed his life why he wasn't coming to the second one. "The economy, man." (ooohkay)
Doing these two conferences was a lot of fun, and encapsulate some of my proudest memories. They really helped cement our credibility at the time. However, it probably cost my partner and I half a year of productive time. Not only did we not make money for the hundreds of hours we poured into our labour of love, but that was hundreds of hours that we didn't spend building our actual business, which more than defeated whatever growth goals we had when we started.
All of which is to say that running a conference is a vanity flex, and it's basically all but guaranteed to lose money unless you have such a large social following (see: XOXO) that it literally doesn't actually matter if you lose money because your YouTube check that month could pay for everything.
So, would-be conference organizer, you have ask yourself two potentially awkward questions: why on earth do you actually want to run a conference, and why do you think anyone would pay to come?
Remember: the easiest way to get $100k running a conference is to spend $200k.
These days in particular, it's incredibly likely that the market is conferenced out. There's just so damn many events people can go to. At some point, a lot of people seem to realize that they don't need to make any new buddies. Invent a way for them to get an uninterrupted weekend of hacking time and you'll be rich.