Lenses are already quite cheap to make. You can get prescription glasses fitted to a knockoff designer frame of your choice in half an hour for less than $50 in e.g. Shanghais knock off malls. You don't even have to bring your prescription, they use a laser device to measure the glasses you brought with you.
Even in Finland you can get basic standard prescription glasses for 59€, or even second sunglass pair for same price(not polarizing though). And the measurements are free too...
Though these are standard material lenses and price really goes up when you want thinner and lighter for higher refraction.
Still, just how cheap something standardised can be even in country with high labor cost is amazing.
I’ve done this in Beijing. I asked for sunglasses and they gave me the lenses and the frame separately, then at the back of the building, some person dipped the lenses in a dark liquid and after drying, put them in the frame for me. Amazing.
