I ran into a 20" monitor one day, a Sony GDM-1952. Hook it up to a PC ... no go. But it can be made to work, as I found out.
Some time later, I happened upon an NCD HMX 20" monitor, in reality an Hitachi HM-4020-D. The Sony pales by comparison.
What they have in common is their inability to display ordinary VGA, and their low cost because of this.