We have a cheaper (and older) LG gas dryer and I don't ever remember hearing much noise from it.  BTW, Home Depot delivery guys don't/can't install gas appliances, so at least you avoided the aggravation of finding that out after the fact.  $400 to install; however, is beyond ripoff.  I hope the plumber wasn't your regular plumber, and if it was, methinks it's time to look for a new one.