Glasses are one I’d specifically advise against spending tons of money on. All of the different brands and designers are all owned and manufactured by the same two or three lens manufacturers for dirt cheap. I can guarantee that the $400 pair of glasses is using the exact same lenses and frame materials as the $40 pair, because they’re both made by the same companies on the same machines in the same factories using the same materials.
The only reason different designers and brands exist is to give customers the illusion of choice. The same way Nestlé owns an entire conglomerate of food companies that are on the shelves next to each other so you can “shop around”, the glasses brands you’re comparing in the store are all owned by the same company.
Glasses are only expensive because those lens manufacturers also own the major glasses retailers, and force smaller retailers to play by their rules if they want to be able to sell their glasses. The glasses only cost ~$10 to manufacture and ship, regardless of the style. The rest is pure markup.
Buy those fuckers online for like $50 a pop. Hell, if you want to spend $400, just buy like six different pairs. Now you can style them for your particular needs. Maybe you have a daily beater pair, then a more classy pair for going out, a sports pair for working out, etc… And they’re all made using the exact same machines that the $400 glasses were made on.
Google Luxottica (which is one of the main lens manufacturers) just for a glimpse of how wide their ownership goes. All of the big optics companies have focused on vertical integration. So they own the companies that produce the lenses, the companies that produce the frames, the companies that market the frames, etc… And they only keep them separate to give the customer the illusion of choice. When you walk into a LensCrafters, it doesn’t matter which glasses you buy; All the money is going to the same parent company regardless.