Upper East Side rich moms practically wrote the rules of polished style. Their secret? Timeless dresses that balance banquet sophistication with errand ease, a combination you can score right on Amazon. These expensive-looking dresses are defined by details such as flowy fabrics, cozy knits, refined silhouettes, high-end accents and tailored shapes. They could totally be from a Park Avenue boutique, but surprisingly, they start at just $15. So if you're ready to look like a wealthy socialite, read on.