Ross-Simons offers its Ross-Simons 18" .33-Total Carat Weight Diamond Sideways Lazy Heart Sterling Silver Necklace for $145. With free shipping via coupon code "APRBD", that's a saving of $213 and the lowest total price we could find. It features 42 round single-cut diamonds, a rope chain, and springring clasp.

Note: This necklace is available in 20" size for $5 more.