Good concept, bad pricing. Not owning your product and selling it at a high markup (starts at cost + ~$20 for small items and converges to 20% markup for more expensive items I believe) will prove to be a non-viable business model. Consider offering some customization, bundling, or outright proprietary products - difficult to do, but that's often the way to own the space. Eg look at Warby Parker and how owning the product allowed them to disrupt the glasses market.