How I spent my summer of 1982: the Making of Donkey Kong for the Atari 2600
garrykitchen.medium.com
garrykitchen.medium.com
Just to put some context on this very true statement, the factory coinbox in these games held around 3200 quarters or 800 dollars. When this game came out operators were cutting the bottoms out of the coin boxes because they were overflowing and jamming the coin mechs faster than they could be emptied.
It cost more than a quarter a game when it first came out, pretty sure it was at least a dollar. Even at that it would still take 13+ Hours which you're right that seems like plenty of time, it's possible the two player games earned faster or the cost per game was higher.
This was also long before cell phones or even pagers were common, so if a machine went down on a weekend it represented a pretty big loss.
The cash that these machines earned was crazy and the distributor conventions (and after parties) held in the 80s were legendary!
EDIT: Actually the conventions and parties up until the mid 90s were pretty wild too! Street Fighter 3 earned 5K a week for the 1st month it came out, I remember converting Asia market games from 220V to 110V just so we could get a jump on the North American cabinets. Cherry Master "Grey" machines were pulling in even more.
The points about communications are huge though. If you didn't grow up during that time you don't understand how different it was just to try to get ahold of somebody at any random time.
I did some looking into DK and it was capable of charging 5 coins per play. It definitely was a different time.
Here is a link to an operating manual, which includes schematics and parts list.
https://www.arcade-museum.com/manuals-videogames/D/dk-tkg4u....
https://dadhacker-125488.ingress-alpha.easywp.com/donkey-kon...