DCL is on to us, folks!! I booked a 9B for the Magic in 2012, but later looked to see if a SPH was available (didn't even look at the price), and 5020 WAS available. Called DCL to change the booking, and the agent said "are you sure? There's only a $10 savings".
So, for an extra $10, I have an unobstructed view now. Crazy.
Actually, I think it depends on the cruise, and what category is selling faster. Plus, as someone else has pointed out, the more fair comparison should be to a Cat 9A as the 10A SPH is on Deck 5, and Cat 9B is only Deck 2 only. For our cruise, the difference from the 10A to 9B is $700, and then another $500 to go to a 9A. So depending on the cruise, there can still be a huge savings.