From your description it is a minor problem with the pin. The computer works, but it is only a coil which is not working (or did I misunderstand something).
The driver board of the P2K is quite easy to fix.
In this case I do not think it is really overpriced.
Especially for the P2K which have "special" parts like the window, the prism card, etc, which are rare and are sold for a quite high price.
He could easily sell the playfield+cards as conversion kit and the window and will get already 2k for this.
But, if it is just the driver board this should simply be fixed, saving another P2K!