The North Sea Farm Foundation pioneers seaweed cultivation in the North Sea. This project addresses the economic prospects of up-scaled production of seaweed, looking at production costs only. Scenarios for future large-scale seaweed production are formulated and evaluated using the EnAlgae economic model. Additionally, Monte Carlo analysis is performed. Based on the findings, we conclude that a significant cost reduction seems possible, with expected cost prices down to €1,200 per ton DM. If all goes well, relatively low-value markets such as the alginate market are within reach. More realistically, a mix of low- and medium-value markets is needed to cover the costs of seaweed production in the North Sea. Current developments show that these markets exist; especially in the food market where seaweeds can be promoted as organic, sustainable and fair trade.