To estimate the insurance and altruism values of a novel hypothetical treatment on survival gains for perinatal-/infantile-onset hypophosphatasia (HPP), a rare, severe, inherited disease, which—if untreated—leads to early mortality in children. Residents of the United States aged 21–54 years from the general population participated in a web-based, cross-sectional, prospective, stated preference survey. The insurance value module included respondents planning to have children, whereas the altruism value module included respondents not planning to have children in the future. A multiple random staircase survey design was utilized to assess respondents’ willingness to pay (WTP) for insurance coverage of the novel HPP treatment offering survival gains. Among the 511 eligible respondents, 50.3% (n = 257) and 49.7% (n = 254) were included in the insurance value and altruism value modules, respectively. Overall, 72.2% of the respondents were aged 30–49 years (insurance module: 72.4% and altruism module: 72.0%) and 52.8% were men (insurance module: 56.8% and altruism module: 48.8%). For generous coverage of the novel HPP treatment, the mean WTP was $10.35/month or $124.22/year as additional health insurance premiums for the insurance value module (insurance value makes 90.1% of the total treatment value). The mean WTP was $9.40/month or $112.85/year as taxes for the altruism value module. The high insurance and altruism values for the novel HPP treatment, which can significantly improve survival, suggest that health gains for children may be valued more highly than similar health gains for adults, especially in a rare disease context. Hypophosphatasia (HPP) is a rare, genetic disease and can be life-threatening in those who have first symptoms at less than 6 months of age. This study assessed insurance and altruism values of a hypothetical novel treatment for children with HPP diagnosed within the first 6 months of life in the United States (US). Insurance value was defined as the value (individuals’ willingness to pay for an insurance policy that covers the treatment) placed on the insurance coverage of the new treatment among adults (aged 21–54 years) in the US general population planning to have children (or more children among those already with children) in the future. Insurance value group accounts for future HPP diagnosis in their children. Altruism value group was defined as the value placed on the new treatment among adults not planning to have one or more children in the future. Among 511 participants included, 257 were in the insurance group and 254 were in the altruism group. Insurance value group participants were willing to pay a monthly premium of $10.35 or $124.22 yearly to secure access to the novel treatment for the future generation. Altruism value group participants were willing to pay a monthly government tax of $9.40 or $112.85 yearly so that other children in the society could benefit from the novel treatment. These findings suggested that US adults were willing to pay additional health insurance premium or tax to have access to a treatment, which improves survival of the next generations in case of HPP diagnosis.