Absorption costing is required by GAAP, so I wouldn't say it is a "trick". But it is important to understand the limitations of the method to really understand the resulting financial results.

Look what happens if you have large changes in production quantity from month to month -- see what happens to product cost per unit under absorption costing vs. variable costing in the example below. If you're a manager needing to make decisions related to production, which is more useful?

January February March Production units 1000 1 500 Variable cost per unit $ Fixed Costs $ 10 $ 10 $ 10 5,000 $ 5,000 $ 5,000 Absorption Costing Variable Costs Fixed Costs Total Product Cost $ $ $ 10,000 $ 10 $ 5,000 5,000 $5,000 $ 5,000 15,000 $ 5,010 $ 10,000 $ Cost per Unit 20 15 $ 5,010 $ es in Variable Costing Variable Costs Fixed Costs Total Product Cost Cost per Unit Period Costs $ $ $ 10,000 $ 10 $ 5,000 $ $ 10,000 $ 10 $ 5,000 10 $ 10 $ 10 5,000 $ 5,000 $ 5,000