Large AND fast storage?
http://www.fusionio.com
(3/2013)
Some (all?) is through PCI-Express slots.
Combo of flash and spinning disks.
They offer both in-machine cards and attached "box" storage solutions.
Costs?!
Low-end card seems available around $10,000. A few for les, and many for much more
https://www.google.com/search?q=price+ioDrive2
http://www.fusionio.com/solutions/high-performance-computing-hpc/
http://www.fusionio.com/products/