A recent email from Alchemy Architects says:

We have now included more and lowered our prices! 2,000 SF weeHouses with Good Stuff are around $125/SF or less, leaving you extra coins to put into your site.

Old pricing was in the $150/SF range, so it's quite a drop. Actual pricing depends on your part of the country.

Also mentioned:

Order a weeHouse SMALL with an off-grid Solar Package before November 1, 2008 for only $99,000 [$109,000 for CA and other states west of Colorado]. Outfitted with Fusion's 720W AC Energy Kit, you only need to provide the foundation, well, and septic to have a completely finished retreat.

Higher capacity solar kits are available for larger homes. For details: FusionModular.com.