There were a number of online eyewear stores that sold online only direct-to-consumer glasses before Warby Parker in the “upscale” price range of $100 GlassesUSA.com (2007), ~ 45% of SKUs are private label Glassesshop.com (2004), ~ 90% SKUs are private label

and many more online stores that sold even cheaper private label RX eyewear: zennioptical.com (2007), 100% SKUs PL, price range $6-45 Eyebuydirect.com (2005), 90% SKUs PL, price range $6-45 39dollarglasses.com (2000), 100% SKUs PL, price $39-109

So, at least part of your argument is unjustified. The guys at Warby Parker created a very unique product perceived at the edge of cool/”retro-intellectual” / boutique-quality / affordable / with a noble mission. That was unique.

For ecommerce, you can't just create a product that solves a problem (Low cost glasses), you also have to create a successful brand. Stand for something more than just a product (or what you're selling). That's why Warby Parker is so successful, because they carefully cultivated a brand while solving a huge problem in a market. That brand affinity is a piece of what they are selling you and what consumers are latching on to (in addition to the fact that they are saving you hundreds of dollars on your eye glass purchases).

Product alone isn't sustainable for the future of ecommerce. This is why I don't think niche ecommerce businesses like Dollar Shave Club / Harry's (shaving) and HelloFlo (Tampons) are sustainable and scalable in the long run. Is it really that big of a problem they are solving and can you really build a brand around it?