For me to find the lowest shipping I ship from my store to my home address, 10 miles. Since I am on the east cost in PA, my highest shipping costs are to FL and or California. So in Pirate ship I would use the 8x7x6 and 4 lbs for the package and my home address for Lowest price, and rates to California for highest. To get an address far from you I use some # and Main St of a city far from me. Sometimes I get invalid address then I use Zillow for an address in that area. Get an average price for the mug shipping then repeat for other items. Now if you are in Iowa for example you would be in the Middle basically of the country and your shipping rates could be lower, or if your in Maine your rates could be higher. All shipping is calculated by weight, size, distance and value of the item shipped so no ones shipping calculations will be the same. This is the hardest thing for anyone to calculate when starting and is the hardest thing for software to calculate in real time which is why it is expensive to add to an online store. The other thing to realize is 1 Mug to ship is more than shipping 4 or 6, since each mug is more expensive to ship individually than 6 in one large shipping box. More calculations to consider.