Jenny bought six cookies and six cupcakes at the bakery. The cookies were $1.50 each but she cannot remember how much each cupcake was. She paid $21 total. How much was each cupcake.

1.50
$12
$2
$2.50

Let's assume the cost of each cupcake is x dollars.

Since Jenny bought six cookies at $1.50 each, she spent 6 * $1.50 = $<<6*1.50=9>>9 on cookies.
Since she paid $21 in total, the cost of the cupcakes must be $21 - $9 = $<<21-9=12>>12.
Since she bought six cupcakes, the cost of each cupcake is $12 / 6 = $<<12/6=2>>2. Answer: \boxed{2}.