One thing you can take note is that:
2x of half price = full price.

Think about it this way.
Half of $10 is $5
2 x $5 = $10

Let's say 10 people pay $10 each, another 6 people pay $5 each.
Isn't 6 people paying $5 each the same as 3 people paying $10 each? Let's see.

$5 x 6 = $30
$10 x 3 = $30

Same :D

Half the number of people pay double :)