Mutually Assured Destruction

So our apartment complex has two units up for sale publicly. For the sake of argument, both units are the same. Same three-room setup, same area, almost identical location. Both sellers have similar motives to move out (Hint: It's a woman!).

One of the apartments started out at a high asking price some time ago. It was a bit dodgy, but if somebody's buying, why the heck not? Then the other apartment came on the market, and undersold the first seller's asking price. To tell you something, it wasn't by much, maybe three percent in all. But it was enough to start a war. The original price dropped five percent overnight. One week later the second seller dropped its price to match.

A third unit came into the market some week later, albeit privately. The rate this goes, nobody's selling. Maybe they should think about collusion or something?