What are the three types of costs?

A simple way to group costs is: fixed (stay the same each month), variable (change with usage or volume), and mixed (part fixed, part variable). For websites, fixed costs might be hosting or a maintenance retainer, variable costs could be ads or per-task content work, and mixed costs show up in tools with usage tiers. This is useful when budgeting a site: separate what you must pay to keep it live from what you invest to grow it.