Because a bag of parts isn’t a functioning device, and things like labor and customer support cost money?
Things like a “nice case” can only be done affordably when you’re stamping out tens of thousands of the things.
Sure, but the full price is $200, which is already in the cheap laptop range. With much more functionality, more expensive parts and yes, with labor and customer support.
ASUS E410 is $159 currently on Bezos' website.