Zenni, eyebuydirect, goggle4u are all in this space and provide cheaper glasses. It seems like new ones keep starting, then slowly raise prices, leaving a gap for a new minimum cost provider.
Eyeglasses are an interesting example of a market failure - customers have been paying 10x the actual price for an important item, for 20+ years, and the market hasn't fixed it.
In Beijing I used to just head down to Panjiayuan Zhaojia Glasses City and get pairs for ~15 bucks. Rest your head on a machine that reads your prescription, pick out frames, bargain, 30 minutes later you have your glasses.
In the US glasses are medicalized, which hides the reality that glasses are really cheap and simple to make; for people without money this causes real harm.