I would suspect is it a wash, think about it (I am sure you have thought it through, but for the benefit of others), double patterning means you have to send it through twice. To get the same output means double the equipment, so if immersion is over 2x more expensive then I suspect immersion would be more expensive, but if it is less than 2x more expensive (over a single pass dry) then double pass is more expensive... I don't know the answer to that one.
It should suffice to say, it is expensive.
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