Ironically, I'd be willing to venture a guess that Amex CENT has somewhere around 1% of the US population. I vaguely remember reading that PLAT had around 6m members and CENT 1-2m. It's come a long way from the days of CENT saying that there are only 10k members worldwide.
I feel like Visa must have something up their sleeve with this. They're not a dumb company, and they know people aren't going to pay $495 a year for two airport lounge visits, some random gifts, or concierge use (unless the concierge is top-notch, and not the usual Visa Signature concierge or the Circles concierge that AMEX uses).
Barclays is a smart and great company, I'd be pretty shocked if there wasn't more to this, other than the card being made of carbon fiber.