@Neko
No, there really isn't a good reason for those scandoublers costing so much. Find an external RCA->VGA box on the web, like for an Xbox or PS2, costs 60 bucks, even very nice ones, some even accept rgb input. I saw one on sale, 4 input switcher to VGA (60Hz) 42.95USD. In EU I suppose it'd work very well with an amiga Scart adaptor (would work with that in US too, just have to import the adaptor and vga box)