Someone help me out here:

"On the north side, Clayco has proposed building two towers as part of the original OGE site plans: a 26-story office tower and a 25-story residential building. On the south end, the company has proposed a 25-story commercial building and a 26-story, 253-unit apartment building. The north towers are expected to cost $250 million, while $280 million would be spent on the south-side towers."

If there are two towers on each side and they are of the same height, why is there a $30 million dollar difference? Is that where the parking is going?