As a general rule of thumb, when I try to value lots like this, I try to value the games only and compare that to the asking price. Older disc based consoles are pretty risky, so I tend to only pull the trigger if the price seems good for the games only. If the consoles end up working, I consider that a bonus.
Of course, this really only applies in situations where getting your money back isn't an option. I'm much more likely to pull the trigger on older used consoles when there is a good chance of getting a refund if it doesn't work.
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Maybe, just once, someone will call me "sir" without adding, "you're making a scene."