One thing that never made sense to me...

Well, they wouldn't leave without Lydia and since it happened after Day O, I theorize they thought something worse could have happened and it strengthened the likelihood they'd see Adam or Barbara again. Not to mention, Delia says, "We're not even sure we want our little secret out" before this. So this would present one more thing to hide from the public other than Lydia's photographic proof. If these thoughts help.

Aside from the money and work they had put into the house, this also gave them the opportunity to get Maxie Dean to come to there house. I forget why he was so important, but they really needed him to come out there, and wouldn't before. But once they had incredibly active ghost in their house, they got themselves there.

After Beetlejuice turns into a giant snake and attacks Otho and the family, why didn't they immediately flee the house and never return?