Just in case the deal comes back again...
I recently bought a 3" full 4lb density memory foam mattress pad with 3 pillows for $155 shipped from eBay.
To be honest, I'm trying to force myself to think that it's comfortable. It's far too stiff to be enjoyable. You don't even really sink into it like you would think you do, judging by the ever-popular picture of the hand sinking into the foam. Your weight is so spread out, even by sleeping on your side, that it's like sleeping on a board.
Just my 2c in case someone is thinking of buying one with that density.