Forums like this are the best place to get a feel for prices. Watching for sale threads, talking to as many people as you can. Prices change frequently and quickly depending on supply and demand of particular machines. I would talk more with Warlock. He won't steer you wrong and he knows the older games that you're looking for better than a lot of people. If he doesn't have what you're looking for, he might be able to help put you in touch with someone who does.
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