Right now Target has the AT&T GoPhone $60 Pre-paid Cell Phone Refill Card on clearance for only $18.48!  It’s not available online or for store pickup (it’s a clearance), but shows in stock at all my local stores (DPCI 080-10-0347).  Click on the See Low Price in Cart and the $18.48 price appears.  Since you can’t pull up the cart on your mobile device, I suggest printing out the screenshot.