I've noticed that computer_preservation tends to post high BIN prices, but they tend to be quite negotiable.
If you develop a relationship with them, they are very reasonable. Open to negotiations as you said, especially if you get several things at once. I've gotten quite a lot from them.
They have an advantage over many of us because through their contacts they find large lots. They've bought out the entire stock of several companies. If there are certain things that you are looking for, they keep a list and are good about keeping an eye out for you. They're not averse to taking parts from several partially working machines to combine into one working one for you and only charging for the one machine, not all of the donors like you would from most places even though it leaves them with several non working machines that it will be harder for them to sell.
It really does seem like their focus is to preserve as many fully functional machines as possible AND see them in active use, not tucked away in a collection.
