The appraisers use the MLS for comps, I believe. So a bulk purchase would not register. Actually, I think any sales contract can stipulate that the sales price not be made public. It may be at the country recorders office, though. Not sure.
But the bottom line is that REO buying specialists and bulk buyers are getting houses at 30% of their outstanding debt…or lower. This is dangerous for all those who are taking advantage of the 3% down FHA deals to buy from these guys.