kakaku says the LP-Z5 lists for 280,000 yen and the LP-Z2000 lists for 360,000 yen. In Japan the Z5 is advertised for 41% of this list price. Of course there are all manner of problems with actually buying one in Japan, but its just a benchmark. There is probably some percent number one could use to estimate selling price in Europe. As a rough ballpark, we could say that the Z2000 will settle down and cost 30% more than the Z5, whatever you happen to be paying for it in pounds, euros, dollars, or yen. At that rate, I think you can imagine what will happen to the 720p market. I agree with the OP, this will could really blow this sector wide open. Once they get enough supply and prices settle down. Most if not all of the half a dozen new 1080p projectors use the same Epson D7 panels so lets hope those are in abundance.
I would also speculate that the slew of cheap, competing 1080p projectors will have a knock-on effect on the 720p market, hurrying it on its way to inevitably becoming like the 480p market. This is why, foreseeing this, manufacturers of panels and boxes alike did not put much effort into 720p this season (e.g. no Z6, though the AX200 is one bright light), and it will only decline further. I think it might take until early 2008 for the panel supply to ramp up, and the Christmas demand to die down, but that is my roadmap for the future.