2gb vs. 8gb in today's market is a matter of a few bucks. Would you buy an 8gb hard drive today, assuming you could even find one? A 40gb will run you $80 retail at somewhere like Best Buy and it's the smallest they've got. Even if it runs $2/gb, it's a $16 drive (and, because there is no demand for an 8gb drive, of which there are a large supply, they're going to be cheaper than that). A 2gb at that rate would be worth $4, saving a meager $12.
And, even with this savings, MS wouldn't price them any cheaper since they admittedly lose money on the consoles just like Sony and Nintendo. They may have priced them down to $200 sooner or offered the package deal sooner, but it would've been the same price at launch and the same price now. If the market says $150-$200 for a game console, then that's what is going to be paid.
The 8gb hard drive allows for more save information and - with games actually designed to save multiple times on the same storage device - prevents the need for yet another $30+ being spent by the purchaser.
I'm a little shocked when I realize I spent more for a PS2 with two games, two controllers, and a memory card than I did for an Xbox with two games, two controllers, and a built in hard drive. That only gets worse when I realize I've bought three memory cards now for the PS2 and it still only has 3% of the storage capacity of the Xbox.