CashFor/4ComputerScrapUSA is a sideline/front for CJ Environmental, a refiner in MA. They aren't exactly racking up the positive reviews from customers or the BBB. I haven't dealt with them for precisely that reason but maybe that's just ancient history. Ewasted, one of the forum buyers, has nothing but positive reviews and I (and many other forum folks) can speak to their quality of service and pricing.
Also, unless you think you have months of free time ahead of you for d-man and
eBay postings, unloading them all as a freight lot is probably your best shot to recoup cash. You could be sitting on 1200 eaches of carefully extracted parts for quite a while if you want to sell that way. That's a bit too long-tail for my tastes. Or, you could go halfway; pull boards and drives to sell in bulk and then move the rest as scrap ABS and steel.
I think your first step is a decisive and realistic assessment of your ability to commit any and how much time to this massive intake. From there, start talking to the buyers who can best facilitate.
Bookmarks