Unfortunately, nobody wants to change this because insurers love charging premium rates for low risk recurring costs, providers love obscuring their prices, and consumers have come to demand their insurance covers “the basics”.
I actually got a pair of prescription tinted (as in sunglass tint) aviator high-index frames w/ lenses for about $110.
There was a site, myopticalshop.com that could do high-index rimless for $150, I haven’t checked in awhile, though.
[edit]
So, the rimless frames are $50 and 1.74 index lenses are an additional $129.
You can get polarized glasses from Amazon for $20.
Zenni gets you in the door with a low base price then slams you with the add ons.
If you have a reasonable Rx, Zinni are likely using finished lenses. Polarized have to been surfaced in the lab.
However, it's not for everyone. For one, it's out of network for insurance providers, so you have to deal with paperwork yourself and the deductible is high. Also since they are online only, you have to adjust it yourself, which isn't always easy. And being online only means you can't try it on beforehand.