Based on the first link...mercy. Train wreck from beginning to end by people who had no idea what they were doing and just kept digging themselves in deeper and deeper until it was far too late.

I knew a guy in Doctor Who fandom back in the day who ran a convention with a ton of guests (it's where I met Jon Pertwee right before his passing), held at a high school. He lost a ton of money on it, but he decided the best way to make it up was...to run a SECOND convention!

Last I heard, he'd lost everything--house, car, job--and had to move his family back in with his parents.

So if you ever get the idea to run a convention, and you have no experience, do the smart thing...let someone else go first.