My last pair of designer frames with lenses from LensCrafters: $350, similar pair from my optometrist: $750, similar pair (but not designer frames) from an online retailer: $50.
In industrial supply chain, if you have two suppliers who are each charging the same price and you know that one is making higher profit margins, go with the one with higher margins - they're more likely to be stable.
I'd rather deal with a company that ploughs surplus back into salaries or R&D or even charity than squandering it as profit.