I don't know much about this stuff but assume it's worth somewhere in the 5 digits. He has a LOT of stuff there. Of course a ton of old shit, too, but seems like a lot of collectors' items and it would be good in a gaming museum (they do exist, rarely). He's certainly put tens of thousands into it.
My guess is he got married, had a kid, and his wife told him to dump this stuff. A guy who's buying three game boy advances simply to have them in different colors is really beyond collecting and into hording IMO. I realize it's a gray area differentiating.