These non-reference 5870 cards are such a good deal because you can increase their voltage using a pencil mod for big overclocks (e.g., 1040 MHz on stock cooler). But everyone thinks the cards can't be overclocked because the cards don't have a software controllable voltage. So I bet the stock built up and now Newegg wants to dump them.
Great to take advantage of that market situation - buy it cheap and know you can overclock it just like the reference cards, you just gotta use a pencil to increase the voltage (erase the pencil shading if you want to put the card back to stock voltage).
Or just keep the stock voltage; my non-reference Sapphire 5870 has no problem running at the maximum AMD Overdrive setting of 900/1300. But I'll be doing the pencil mod once I get my active displayport driver for eyefinity, so I can try to break the 1000 MHz mark at around 1.23V or so. The instructional website linked earlier (bottom of page 2 of this thread) explains the target resistance you are looking for when shading with the pencil in order to enable overclocks that break 1000 MHz on stock cooling.