The LGW spotting area had a cafe which sold really lovely coffee and cake if I remember rightly, a play area and a learning area and a shop. You had to pay to get in. It was always packed, so I imagine it turned a profit.
The Sofitel and Bloc now have rooms you can hire out specifically for spotting at about £50 a day, so they really are missing a trick by not having their own spotting area.
I spent many happy days as a kid up there. Here's some nostalgia:
https://www.youtube.com/watch?v=uWw7SnjOGug