PCB assembly costs why would LCCs and/or QFN packages double the cost?

[splin]

I was just looking at the PCB assembly cost estimator at www.PCBShopper.com. 1K boards with 30 unique parts, 100 SMD parts comes out at $910. Change to 99 SMT + 1 BGA/QFN/LCC part and the cost doubles to $1880.

That's a big difference; I understand that BGA handling can be expensive but what about QFN/LCCs? Aren't they pick and placed and reflowed like any other SMT board or do they require the board to be processed on a different, more expensive line?

Do all (most at least) BGA designs require XRay testing after assembly and is that likely to be included in the above pricing? Do QFN and LCC designs also require XRay testing?

[EDIT] Doh! Just looked at the order page of one of the quotes - PCBCart. Against the 'number of BGA/QFN/LCC parts field' there is a roll-over help pop-up which makes it clear that all these types require X-ray testing.

That does make me wonder why so many parts are only available in leadless packages even for relatively small number of leads - for example the AD5780 is only available in a 24-Lead LFCSP_VQ package.