Here are several Bally price sheets from the late 1950s. As 
bingopodcast explained, the games were expensive. They were good earners, and they had to be since they were subject to confiscation in many (probably most) of the jurisdictions they were operated in. Imagine the earnings your games would have to generate to risk losing, say, a half-dozen or more bingos in a police raid. One interesting tidbit is that operators often made cosmetic alterations to games so that police, often armed with just a list of prohibited game titles, would not recognize a relabeled bingo. I've attached several photos of disguised games. My favorite is "Bingo Gardens," a relabeled Cypress Gardens. I think some operator had a wicked sense of humor with that one. I remember playing a magic squares game in Las Vegas in 1976 - I think it was Broadway. That would have made the game 21 years old when I played it, and I'll bet it was operated continuously during those 21 years. Bally did strive for immortality, and the games were engineered accordingly. There is a commissioned history of Bally, "Bally: The World's Game Maker" by Christian Marfels, but it sticks to Bally's up-and-down corporate history and it doesn't go into the technical details you seek. It does mention bingos and Don Hooker, and it states that Hooker was on Bally's board of directors at one time! I was unable to find any other books authored by Marfels, and after reading his book, I think I know why. There also is a one-hour audio interview of Don Hooker somewhere on the internet. You should be able to google around and find it.
Bally Cypress Gardens with name altered to read "Bingo Gardens," seen on Craigslist 2018-07-30 (resized).pngBally Gayety bingo pinball backglass retitled as "Big Combo." 3-L scores as 4-L not an original feature of Gayety. Seen on eBaBally Price List 1956-03-15 Night-Club and Crosswords (resized).jpgBally Price List 1960-06-01 Laguna Beach (resized).jpg
Okoboji, IA
