My comment is solely based off of how vicious Sony is regarding hardware pricing, sans PS3 of course. I think they want to undercut Xbox even if the losses will be great. Let's just wait and see what happens. I'm not an insider, just thought this would be interesting and if they'd consider doing that. Of course this all relies on how much of a loss Sony wants to take. But like Trunkswd said, a digital at $399 does seem more feasible if Sony wants to keep a $399 system on the market.
Sony had other cash cows back in the day and wanted to promote their optical media with PlayStation. Very different situation.
Maaaybe the digital will be $399 if they're feeling specially generous, anything lower seems just unrealistic.