Money, of course, was needed by them.
Even Qi Cultivators had needs, and often greater than those of mortals.
Just like mortals, given the opportunity, they would surely live in large houses and have meals with fish and meat; who would choose to suffer if they could enjoy luxury?
Someone like Skeleton Wanyan ate Ringing Cauldron Food and resided in a place where he could freely expand vast open spaces, otherwise, his state of mind could be damaged.
And to pursue such things, money was indeed necessary.
Wealth and resources, regardless of the Righteous Path or the Demonic Path, unless one was from an ascetic faction, all would find ways to amass a great deal of money, even resorting to robbery.
And who says ascetics have no money? They only practice Dharma Technique ascetically, living in poverty, but living in poverty doesn't mean truly being destitute; sometimes maintaining a facade of 'poverty' also requires money.