If there were a console that had only one interesting game, and I didn't expect it to get any more interesting games, there's absolutely no chance that I would purchase that console for more than about $50.
But, this is pretty far away from reality, as every major system ends up with more than one game that would appeal to just about anybody. A more reasonable topic would be something like "How many exclusives does it take to make a console worth buying?" And to that question, I would say that I'm willing to pay about $300 for a system that I'll get six good exclusives out of. If the system were $500, and it only had six interesting exclusives, I'd probably only buy it if I expected it to also be good for third party games.