I don't see them being wrth what the bids have hit, obviously some people think they are though.
The reasons I don't see the value is simply because of the cracks and corrosion, and who knows what damage the rust has done in the transmission area. (red oxide = HUGE expansion) by the time you have them repaired you will have another $1000 to $2000 into the cases alone.
Also, judging by the rust and oxidation, it's a very good indication that the thing was sitting outside with water in it, does it freeze where it was? (salem oregon? I'd say YES) If so it's a fair assumption that the cases themselves have been distorted by ice.
And after putting all the money into the cases, collecting parts to build an engine with them, and collecting all the frame peices, you still will NOT have an 'original' sandcast bike, it will be an assembled bike with expensive parts. (something that for some reason doesn't seem as important to the sandcast crowd, try selling any other 'assembled' vehicle as an 'original' and you'll often end up in court)
ken