Until November 24 at 1 am ET (or 100% claimed), Amazon offers its Amazon Prime members the AmazonBasics Silicone Case for Apple iPhone 4 and 4S in White (pictured), Pink, or Red for $9.99 with free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs around $5.) That's a $5 drop and the lowest total price we could find. It fits the iPhone 4 / 4S for AT&T and Verizon.

Amazon Prime membership is $79 per year; however, Prime is free for college students for six months, and free for parents and caregivers for three months. (Note that currently there's a waitlist for Amazon Mom.)