100% true. I change my glasses annually and over the past 5 years or so, have shopped at a large Canadian chain that has literally 1,000's of frames in-stock. They have everything from $29 specials to separate little rooms they call "boutiques" individually displaying Prada, Chanel, Versace and D&G, as well as a separate Oakley and Ray-Ban sunglass "boutique". I've spent hours and hours and hours over the years trying on and choosing pairs. Seeing them up-close, feeling them, really evaluating them first-hand.
I can assure the OP that virtually all the designer styles are replicated over-and-over again in the less-expensive lines. They all roll off the exact same production lines - the quality is really no different. How can it be? Plastic and wire is plastic and wire. I don't begrudge anyone who gets personal satisfaction out of owing "brands". It is impossible for anybody but the owner to tell the difference though, without the visible badge.