It's so the "starting at" price is low but they can mark up RAM and Storage upgrades when you actually go to order as if they were the expensive piece. They are making something like 80% margin when you max out the RAM, I assume similar for the "SSD storage" of ambiguous type.

Dell did the same thing with the RAM in a 7740 and 7750 I recently ordered (work and personal), ironically about the same markup.