I'm pretty sure he's had that ebay ad up for like two years now.
Yes, it's all cool stuff but what can one do with it all? At 500 grand, you won't buy it to flip it for a profit.
He'd be better off selling it by the piece or in small lots. Like pairs of matched tube amplifiers or the bunch of 8 JBL 18's.
Some of the stuff is worthless like the "home brewed" Dynaco amp.