The term dual place breast augmentation is simply a technique and term that plastic surgeons use to describe how the muscle is treated during your breast augmentation.  There should not be an additional charge for one technique over another.  The most important thing to consider in any breast augmentation is first your safety and second the implant and its safety profile.
Make sure that the surgeons you are seeing are truly plastic surgeons.  There are many surgeons from different specialties who are board certified, call themselves plastic surgeons, but they are not certified by the American Board of Plastic Surgeons.  One way to know is to find a surgeon who uses Sientra breast implants, since Sientra will only sell their implants to truly board certified plastic surgeons.