I weighed each one individually and they actually weigh 7lb 8oz each.  I have found that every set of weights that I have put on the scale has not been accurate with the exception of one brand (Gaiam).  I thought that was interesting.  There is a small break in the vinyl.  On the postage, please look at all the options.  Sometimes it is cheaper going priority, but sometimes it is UPS or Parcel Ground... depends on the zone you are in.