Woot! New pants are my favorite thing!
Lbs. per size is a pretty individual thing. It's all about how your weight is distributed and where you lose first. If you ask ten different people who weigh 250 lbs what size pants they wear, you'll get a range of sizes. A perfect example: One of my close friends, who is the same height as me, was wearing a size 24 when she was 225 lbs. I am 252 and wear a 20.