> but it would invite a secondary market for these cards

There are already markets for fake IDs, so unless you're suggesting that small local restaurants purchase scanners to confirm the authenticity of each ID, it would be relatively easy to circumvent this check too. (Some states require IDs to be scanned for selling alcohol, but many, e.g. in Oregon, do not, and the only check is some employee looking at a card in their hands for a couple of seconds)

> Plus having special cards feels corporate

Not at all. Plenty of local restaurants in my are (Portland, OR) have rewards cards, where you get stamps and a free meal after some amount of stamps.

The high prices would be to ward off these one-time customers who are only there for the single instagram photo. If someone is invested enough to make a fake ID just for cheaper burgers, presumably they're going to be repeat customers that develop a relationship with the restaurant, which is what he wants.

Isn't the mere possession of a fake ID illegal where the restaurant was operating? Whereas buying a coupon from someone isn't.