The current Opteron that's out right now is $800.
They'll definitely go down steadily as the Pentium 5's and late ClawHammers arrive, however. As usual, you gotta pay to kick ass. Hopefully they'll get one down to $200 or so. The lower-end Opterons (1.4 GHz) are about $200 right now, so maybe we can expect better prices in a month or two.
-Lasereth