Marginal Cost is a finance/economics concept used to analyze decisions, risk, or performance. The key is what changes when it moves up or down-prices, cash flows, risk, or incentives.
Example: You might use Marginal Cost to compare alternatives and choose a plan.
Related terms: Money Supply (M1/M2), Price-to-Book (P/B) Ratio, Loan-to-Value (LTV) Ratio.