The times to resolve the bug in code may not be significantly different at all. In the 1967 to 1981 period cited, the expense isn't putting it in the main branc

The times to resolve the bug in code may not be significantly different at all. In the 1967 to 1981 period cited, the expense isn't putting it in the main branch of your repo and letting your pipeline put it everywhere. It was putting it on tape or disk, sending it to a customer, sometimes flying your own technician to the customer's site, installing it, maybe performing a backup beforehand, letting your customers know this is all necessary, publishing errata in a physical manual, and convincing these customers you still take quality very seriously.