This G15 is the Oldest Running Digital Computer in America [video]
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I can't wait to see the kinds of programs we can run on a machine like that, along with discussions about tricks when writing programs for serial memory computers :D
Wikipedia says it could be rented for $1485/mo, and the average salary in 1956 was $3600 or $300/mo, so it would have to replace 5 people (engineers must have earned more), if you don't count the extra cost of software, power, and maintenance.
I remember from a book on Richard Feynman that a classroom full of bright students was about as fast as the computer the Manhattan Project got, except, of course, the computer didn't get tired.