Since I haven't shipped using ground shipping in the US, here are a few tips and guides I found for you -
Link hidden: Login to view - I particularly see the possibility of getting cheaper rates in the suggestion on this post, but it would be best to check to be sure :)
Link hidden: Login to view
Link hidden: Login to view - Another reason the rates you are getting may be higher than usual could be the 10% (residential surcharge) added if you are having your pallet delivered to your residence as pointed out in this article.
Hope this helps. All the best :)