At some stores you don't even need your prescription. I recently purchased my best (and cheapest) pair while visiting Japan and an eye exam was part of the transaction - at no extra cost! As an American I was shocked at how seamless and quick I was able to walk out with a new pair of glasses

I've done the same. Did the eye test in English with really big writing on the cue cards :). 40 minutes later my glasses are ready. Real contrast to Australia where you make an appointment for an eye test for a day or two later. The test is paid for by the government (Medicare AUD$56.80) and then select your frames (AUD$150 and up) and then come back a week later. I suppose the delay justifies the cost or vice-versa.

Postscript: My Japanese friends tell me they get their glasses from South Korea, because they're even better.

On a vacation, or online and shipped to them?

Same here. I just moved from France to Tokyo last year and I bought a new pair (same characteristics).

France: 380 EUR, including cheapest frame (80 EUR), regular lenses and ophthalmologist (80 EUR). (I had no health insurance.)

Japan: 10800 JPY including pretty good quality frame (5000 JPY) best lenses from the store and no ophthalmologist.

In France, it is not uncommon to have a 500-1000 EUR pair on your nose. Not because people are wealthy, but because they have the health insurance which pays. The first question a glasses store clerk asks is: "Do you have your health insurance card, please? We're gonna check how much we can spend".

Was about to post this. Budget brand eyewear stores like JINS and Zoff are everywhere, and they provide glasses at around $50-100, eye exam included. I've bought several glasses from JINS over the past decade or so and had no problems with any of them.

I wonder if the San Francisco JINS store is priced the same, or they try to make themselves look like a premium brand like how Uniqlo does?

Same here in Taiwan. Some stores like Jins and Owndays are everywhere nowadays.