Prescription sunglasses can cost as little as $25 and as much as $6,400 or more if you buy a designer brand. (Believe it or not, the most expensive prescription sunglasses in the world sell for more than $400,000). Factors like the brand you choose, material, prescription grade and adding additional features, such as polarized lenses, anti-scratch lenses or anti-reflective (blue-light blocking) coating, can run up the cost of your prescription sunglasses.