Check out this article on Malta doing a pay-for-EU citizenship scheme:
"Critics charge that the program undermines the concept of European citizenship, potentially poses security risks and provides a possible backdoor for Russians seeking to escape sanctions against their own country."
From personal observation: Benefits are tangible and immediate to the city and its politicians from increased taxes and whatever bribes are paid, downsides are intangible and long-term to the city residents who get priced out of their homes, lose business because these "residents" don't actually live in the city, and have to live with sometimes-unpleasant citizenship tourists that are often involved in fraud of one sort or another.
