Understanding the Big Data Appliance is a little harder than the other appliances. While it was prominently featured on the appliance row outside of the keynote hall, it was not only off the entire show, it was, in fact, a piece of paper inside of a rack.
Here is what was publically announced:
The Oracle Big Data Appliance is an engineered system optimized for acquiring, organizing and loading unstructured data into Oracle Database 11g. The Oracle Big Data Appliance includes an open source distribution of Apache Hadoop, Oracle NoSQL Database, Oracle Data Integrator with Application Adapter for Hadoop, Oracle Loader for Hadoop, an open source distribution of R, Oracle Linux, and Oracle Java HotSpot Virtual Machine.
Here is what I was told by an Oracle employee manning the booth:
Optimized for lower-value data, Infiniband to move data around node-to-node, Infiniband to move data machine to machine, Not shared disk, Each node pre-configured to run hadoop and Oracle NoSQL, There is nothing that can be done on this machine that couldn't happen on Exadata faster, its a matter of cost
It looks more like a virtualization work load machine (aka VCE vBlock or Dell vStarter) than their existing servers.
Price is a real key here (otherwise, just use Exadata for this sort of workload) and there is no announced pricing. The upper-end of likely pricing would be set by the Exadata expansion server - 750K/rack. The lower-end would be set by commodity hw approaches which I estimate around 350K/rack (Dell, CorAid.) I'd assume pricing will vary wildly depending on what else you are buying and how your rep is doing with his quarter...