Been buying glasses from Zenni for years. Yes, their prices are legit as stated on their website. They do charge a lot for extras like progressive lenses and tints/polarization, but it's still cheaper than most any optometrist I've seen. But yeah, their <$10 frames are kind of cheapo, as you'd expect. But every pair I've ordered came with a hard case and a lens cleaning cloth. Lately, they've been incuding a device to measure your pupillary distance, too. Oh, I haven't tried it yet, but they say you can upload a photo of yourself to use in their "try it on" window.
But if all you need is a cheap pair of single vision glasses, they work. They are made in China IIRC.