Hydrogen valleys, which integrate renewable energy sources, hydrogen infrastructure, and end-use applications, play a crucial role in decarbonizing industrial energy hubs. However, the large-scale deployment of hydrogen is constrained by limited renewable electricity availability and high technology costs. A key insight from our analysis is that the merit order of hydrogen end-uses is dynamic, evolving with an increasing Social Cost of Carbon (SCC). When the SCC surpasses a threshold defined by the Social Opportunity Cost of Abatement (SOCA), allocating hydrogen to the most emissions-intensive sector becomes socially optimal, even if that sector has a higher sectoral abatement cost.