Costs that dance up and down based on how much you produce or sell, like that friend who’s always changing plans. Think materials, labor, and shipping—basically, anything that likes to keep you guessing. Unlike fixed costs that sit there like couch potatoes, variable costs are the unpredictable party guests of your budget, fluctuating with your production levels. Mastering these costs is key to pricing your products right and keeping your profits from going on a rollercoaster ride.