I found a nice condition Rodenstock Rodagon 50mm F/2.8 (looks like the current model) enlarging lens selling for $75. What do you think of the quality and the price?
Should be an excellent choice. Patience might bring you little better price for the Rodagon or a similarly excellent El-Nikkor 2.8, but if it's a lifetime investment for you and shipping issues can be avoided, I don't see any problem with the $75 involved.