As I said in another comment, El Buli solved this decades ago by setting a chunk of reservations aside for locals from the town they were located in and another chunk only for people from Spain. Just do that and add a portion for friends and family.

I used to do consulting for a extremely high-end hotel where a single night could easily cost $3k+. Every employee got to spend a night for free every year and they got a number of friends and family discounts that were 90% off.