Vila initially hadn't thought of so many things... It was only when she was discussing this task with the 'Young Master' that she realized, to construct this Great Wall, she had to pay a huge sum of money to the Undead Tribe to issue the construction task... To make the Undead Tribe willingly work, William had always kept the construction task's bonus quite high. If only calculating in gold coins, the amount the Undead Tribe earns in a day from building houses far exceeds what they get from completing regional tasks.
The regional task rewards are mainly merit points that can be exchanged for equipment tools... With billions of undead each having their preferences, naturally, some prefer to earn more gold coins, which easily resulted in different choices.
But this brought a huge problem for Vila... The poor Fairy Queen counted the gold coins in her wallet, and although constructing the Great Wall was still affordable... spending it all so quickly, what would she do in the future?