Amazon offers the Ray-Ban Women's Erika Round Sunglasses in Black/Gray for $62.39 with free shipping. That's the lowest total price we could find by $8, although we saw it for $9 less last week. It measures 54mm and features plastic frames.
Groupon offers the Emporio Armani Women's Sunglasses in Beige, model no. EA4009, for $99.99. Coupon code "VISA5" cuts it to $94.99. With free shipping, that's the lowest total price we could find by $20. They measure 56mm and feature plastic frames.