This new listing at The Gretsch in Williamsburg is a killer pad — and the seller stands to make a killer profit. The 2,061-square-foot duplex has a huge kitchen and living area along with two good-sized bedrooms and a home office area. What’s more, there’s a private terrance with Manhattan views in addition to plentiful windows and 13-foot ceilings (25 feet in the living room). All this real estate goodness cost $1,302,341 in 2006. Now it’ll run you $2,500,000. But, as we all know, a lot’s changed in this part of town in the last seven years.