Economic analysis is an essential component of QSD for systems where costs often govern decision-making. Traditional cost and profitability indicators, such as investment cost, operating and maintenance costs, payback period, return on investment (ROI), and net present value (NPV), are commonly used in the literature. To compare products that are of equivalent utility but that were generated from different technologies, 100 indicators such as levelized cost or minimum selling price (MSP) are often used. Both of these indicators quantify the average net present cost of a product over a system's entire lifetime, but they are typically used in different contexts: levelized cost is usually used in the context of energy (e.g., electricity) 101 and (more recently) water systems, whereas MSP is often used in the context of biorefineries. The selection and prioritization of economic indicators will depend on stakeholder preferences. For instance, technology developers may focus on levelized cost to compare against benchmark technologies (i.e., the conventional technologies against which they are competing) Two techniques, life cycle costing (LCC) and techno-economic analysis (TEA), are typically used for economic analysis (e.g., for LCC; 107-109 for TEA). Both techniques rely on the system inventory generated by system simulation. After linking those data to unit prices of cost inventory items, additional costs (e.g., labor, tax, insurance) are included with revenues from co-products (e.g., recovered nutrients) to obtain the total net cost of the system. This net cost can be further normalized to the unit cost of the system product/function (e.g., levelized cost or MSP).