I dont know, before i really wanted a 7-string, even an 8-string haha, but when i grew tired of not finding a vocalist for a kinda project of mine, and started to sing myself, found that i can sing (more easely) in D-key, so i just toned my guitar in D haha
But if you like the sound of the B-string, and have the money, buy it. But to be honest, $200 seems cheap for a 7-S, its not broken or something?? haha