In regards to the cost to bring on a 500k player its a net loss in the short term, even walking away with the B3 trophy. The one thing that might rationalize this type of move, and definitely something i would consider, is the fact that once you've won the B3 you get a lifelong ticket to the annual competition.
I never liked that aspect of the B3 and it might provide enough motivation to take the short term risk and cost in adding these unsustainable players for one game or two.
"Well, no ones gonna top that." - http://tinyurl.com/noigttt