Kalman Reti, the Last Symbolics Developer, Speaks of Lisp Machines.

[liam_on_linux]

"We took about 10 to 12 man years to do the Ivory chip, and the only comparable chip that was contemporaneous to that was the MicroVAX chip over at DEC. I knew some people that worked on that and their estimates were that it was 70 to 80 man-years to do the microVAX. That in a nutshell was the reason that the Lisp Machine was great."

https://docs.google.com/file/d/0Bw4Wz8Ir0pl1cmNRaHYwdU1wdXM/edit

Source: http://www.loper-os.org/?p=932