I am sure you know this is a gross oversimplification. There are many reasons to get other then a pro body such as weight, sync speed and certainly cost.
Originally Posted by lxdude
Also "pro" use does not mean abuse. I have bought a few pro bodies that literally look unused as the cameras were only used in the studio. One was an EOS3 used for product shots and the other an F3 used only for copy work. Another benefit to buying pro equipment is that they typically have already written these off so I picked these up at considerable cost savings.
Here is a good price reference -> March 1978 Adorama ad