A best bet is the 6.5-Total Carat Weight Amethyst Heart Pendant (pictured) for $69.99 with free shipping. That's the lowest total price we could find by $65. It features 35 amethyst stones and comes with an 18" sterling silver chain.
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.)