Thanks for the chapter.
Just to straighten things up, secret menus are a common thing among all walks of service-oriented businesses, not only the dodgy ones.
Leaving aside many introduction-only stores, like traditional sushi restaurants (where all of the menu is the secret menu), many stores offer secret menus that are available either for regulars only, through introduction, for big spenders or just asking for the item/service (either by knowing of its existence or by chance). It's just that dodgy establishments have dodgy secret menus.