I think the clerk got the number correct but not the business term. Instead of 40 "percent" he should have said 40 "gross margin points" or just "gross margin."
Here's the math: (selling price - cost of goods)/selling price
$542 selling price - $325 cost = $217 gross margin dollars
$217 gross margin dollars / $542 selling price = 40.036 gross margin points
By the time you factor in all the other costs related to running a business they are actually working on a rather thin profit. The best way to get their prices down and still make a profit would be to improve their purchasing strategy.
And yes, I play the corporate game during the week. Sometimes it's hard to shut it off.
