The article shows how much money is needed to provide safe sanitation for everyone in five cities by 2030. The researchers looked at different ways to estimate the costs, including helping low-income families pay for toilets and waste services, and expanding city waste systems. They found that sewerage is the most expensive option, followed by container-based sanitation, onsite sanitation, and mini-sewers. The total costs vary between 2 to 24 USD per person per year, depending on the city and the sanitation approach used.