Those $500 Dior sunnies you’re eyeing? The retail mark-up is as big as you think it is. Check out this list from the Wall Street Journal of six things you ought to know before you shell out a couple hundred for designer sunglasses.

Reason number one:

“Most sunglasses are made by the same company. Do you prefer the “quality” of Ray-Ban to Oakley? Do you think Bulgari is better than Dolce & Gabbana, or Salvatore Ferragamo is better than Prada? Wake up. They’re all made by one company, Italian manufacturer Luxottica-one of the biggest consumer companies that consumers have never heard of. Luxottica also makes sunglasses branded Burberry, Chanel, Polo Ralph Lauren, Paul Smith, Stella McCartney, Tiffany, Versace, Vogue, Persol, Miu Miu, Tory Burch and Donna Karan.”

Luxottica designs — working closely with designers of each house — manufacturing and branding. It also owns its own brands: Ray-Ban, Oakley, Oliver Peoples and REVO. And they also own the places you’d often buy your lunettes at: LensCrafters, Pearle Vision and Sunglass Hut.

Here’s some insight on pricing:

“The cost of a new pair of glasses will of course reflect materials and labor. But the price will also reflect brand values and marketing-and how much consumers will pay. Luxottica says it makes a gross profit of 64 cents on each dollar of sales. Even after deducting sales and advertising costs, overhead and brand licensing royalties it’s still making 52 cents. That’s some margin.”

Also, don’t think that the high price means greater protection for your peepers. Dr. Jay Duker of Tufts Medical Center says in the article that after $70, most of the medical benefits of sunglasses — UV protection, glare cut-out — tapers off pretty fast.