Since they were originally charging an extra $10 (I think) for white over black during the initial launch, I wonder if it has to do with popularity. Either so they can make a bit more money on the most popular model or so they can try to control demand.
Which is to say, as more of the white get ordered and strain their stock of the white components maybe they start upping the price of that option to drive down demand until they have an adequate stock again.
As I recall the price of white as a case option has gone from $10 or $15 at the initial launch to free and wavered to the $30 mark now.
Bluetooth has varied in price as has the ram and ssd
upgrade prices as I recall.
I don't agree with the practice, but maybe that might explain it... :?