Yes, that would be true. But if you're going to be spending close to $1 million/yr on your cards, spending an extra $50 for that Costco membership would stretch your cash back on restaurants one hundredfold.

If your budget is a lot smaller than that, it's probably better to go with the Costco card, since that doesn't require the premium membership. Ultimately it all depends on what club you prefer and where you typically charge your card.