Their episode of How I Built This was pretty interesting. They talk about how they initially tried even lower prices but found that below $99, people started to question the quality of the product. That could be marketing in and of itself, I suppose.

http://one.npr.org/?sharedMediaId=506455305:506610651

Not sure why this is getting tons of downvotes. Warby Parker's profitability per retail square foot is one of the highest in all of retail mostly because there's such a distance between what their frames cost to make and what they sell them for. Limited choice (Trader Joe's style) and a good sense for the products their target market wants seem to be their secret sauces to pulling off crazy margins on said products.