Like in any other business, anywhere else, there are companies who handle liquidating their assets. They have regular auctions. I've bought a ton of great equipment for my business from them. They have an online auction, you bid and win, if you win you go (often to the failed startup itself) and pick up yoir stuff at a predetermined meeting time. They often have very weird, very specific tech startup things like biotechnology lab equipment, etc. for much discounted prices.