Why does the profit decrease when the sales increase?

A boost in sales does not always lead to an increment in profits. In fact, in some cases, the growth leads to more expenses hence lower profits. There are two main reasons behind decreasing profit even after the increase in sales:

1. An increase in overhead expenses includes costs that occur due to operating a business, like rent and administrative costs.
2. The one-time cost that includes unexpected costs incurred by the business once in a while. For instance, the damage to the stocks due to sudden weather disasters.

Keep these two aspects in mind and evaluate your operating activities all the way through. You'll find the leaking hole that's draining your profit secretly.