For eye exams, I used to pay the optometrist $153 ($117 refraction + $36 dilation). I later found out that Costco often has an optometrist on site in a tiny office and will charge just $50 (and add +$20 for dilation). That's less than half the cost of most other optometrists. A bonus is that the tiny Costco office has no frames so there's no sales pressure to guide you towards his limited selection of frames. Therefore, he always just prints out your Rx and gives it to you without any dirty looks. Costco (the warehouse) has frames but you have to walk next door into the main retail floor to try them. The optometrist has no idea whether you buy glasses from them. You don't need to be a Costco member to use the optometrist at Costco.
For lenses, I used to always pay ~$400 for 2 pairs of glasses. For Eyemasters, Lenscrafters, Visionworks, etc, it didn't matter if they had "2-for-1 sale on lenses" or "2nd pair frames free". The total (when including desirable features such as AR coatings, etc) always came to ~$200 for each pair. I've come to believe the sales promotions at eyewear chains are as meaningless as the "sales" at mattress stores.
Now, I buy from zennioptical.com. Each pair is always less than $35. That's even cheaper than Costco and Walmart.
I think my recommendation won't work for people who are very sensitive to fashion and want to try all the stylish frames at their fingertips. (Ralph Lauren, Calvin Klein, etc.) At my age, eyeglasses are just functional things and I'm fine with picking out a no-name classic style from zenni.