It is based on the current 'difficulty' .

I.E
To get the PSU sorted out so that the boards last long enough to get out of the guarantee period before being returned.
As they ramp up production, they will find that significantly more of the product fail to meet expectations or the 'spec' that has been sold to customers (hence the 'dropping' of the hash rate but doubling of the price per unit)

It is the same with any manufacturing operating, however BFL's previous experience counts for FA because they were working with already developed product (FPGA), manufactured to military specification (xilinx biggest customer is the military, anything that does not meet the standard is sold 'down' the supply chain), what this means is the product is F***ing reliable in all but the most abysmally designed products,You can even stick their products upside down and 'dead bug' them with a shitty PSU  and they still work.....
as a result a manufacturer does not get any 'real world' experience in REAL hardcore manufacturing and fault finding.(sticking a  public domain design based on military spec parts in a flashy case does not make you a design expert or 'crypto specialist')


This is relevant because the BFL ASIC is not in this class of design or specification, so it is going to be a complete bitch to rein in...
What does this have to do with your question.....

Well if you are near the front of the list... then you get a unit and you can mine until the fucker breaks down.. send it back and get a 'new one'.. if you are later into the list... good luck on getting a unit.

However if they can crack the current issues they are having.. then all will be well in happy land.