Fixed vs Variable Cost
Fixed costs do not change with output (rent, salaries, the cost of writing a book), while variable costs scale with each unit produced (raw materials, packaging). The ratio of fixed to variable cost shapes pricing, economies of scale, and how vulnerable a business is to demand shocks.
In microeconomics, total cost decomposes into fixed costs and variable costs. Fixed costs are independent of output over the relevant horizon: factory leases, salaried headcount, the cost of developing a film or writing a software package, regulatory compliance. Variable costs move with each additional unit produced — raw materials, hourly labor on a production line, energy per kilowatt-hour, packaging, distribution. Average cost falls as output grows because fixed costs are spread over more units — the standard mechanism behind economies of scale. The marginal cost (cost of one more unit) tracks only variable costs in the short run; in the long run, when capacity has to expand, fixed costs themselves can step up. The ratio matters strategically. A steel mill or airline has enormous fixed costs and significant variable costs, so it must run near capacity to be profitable and is brutally exposed to demand drops. Information goods sit at the extreme: nearly all cost is the first-copy cost, with variable cost per copy near zero — see Marginal Cost of Digital Reproduction. Cloud infrastructure flips part of this story by converting traditionally fixed compute and storage costs into metered, usage-based variable costs. Distinguishing fixed from variable cost is also central to break-even analysis and to the contribution-margin reasoning behind pricing decisions.