Many years ago I went to get my eyes rechecked and they quoted me around $300 for the glasses. I found a place online and got 3 pairs for just over $100 and that was years ago.

I have had laser eye surgery since then and don't need them anymore but I would say cut out the middle men and buy online.

Also get your prescription from the optometrist and make sure they give you your Pupil Distance. It is important for making sure that the proper focal point is centered. Some optometrists will skip putting that measurement on so you will get glasses from them. Though iit can be measured with help from a friend and a ruler.

As an aside I suggest you put in a complaint to the Costco, they usually take pride in having great employees that stick around long term so they would probably want to move employees along if they give bad service.

Forgot to add the site I used it was goggles4u.com