Having very high-capacity hard drives is one thing, but having those drives certified by the manufacturer for a business environment is another. Not that HDD are failing left and right, as the staying power of disks overall is pretty high. That said, Western Digital has today announced the addition of a new unit into their "RAID Certified" class of drives.
Their new WD RE2 750GB SATA unit is more or less the same as their existing 750GB offering, with the exception of a few new features intended to increase the resilience of the drive. That leads to them giving it their "RAID Edition" label, along with a higher MTTF rating than comparable drives.
For the size and certification, the drives are not all that expensive. The listed MSRP for these 750GB units is $265, more than standard 750GB offerings but not by a terrible lot. The press release does not indicate when, exactly, the new units will be available.