I know they said they were aiming for cheaper than a Xbox. Also don't forget this is the MSRP so who knows what the stores might put the box on sale for. I bought the InfiniTV4 from Newegg when they had it on sale for $229 while it was $399.
I have seen them before for hardware betas.
I think it is also a way to eliminate those who want to play with the Echo rather than test since the testers who pay will have more of an incentive to report issues.