50% off $500 = $250. You save $250.
Equation: $500 − (50% × $500) = $500 − $250 = $250.
Another way to read it: you pay 50% of the original price — that's $250.
$250. The discount is $250 and the final price you pay is $250.
You pay $250 (before tax). That's $500 minus a $250 discount.