Let's say a company is selling sodas for $1.50 and making $1.25 profit per can. Then I come in as the new CEO and order prices lowered to $1.00 per can. Now, our profit margin will go down, but what happens to our sales volume? It goes up, and once it goes up enough our total profit will exceed the total profit the company would have achieved by keeping prices the same.
Just consider taxes "prices."
Coop - that's a great analogy that people will understand. However, it assumes that the demand for sodas is elastic enough to increase volume to a point that the increased sales offset the decrease in price.