This depends on the size of the shoes, what they are made of, and the box. Based on my experience this is what you should expect.
If you are ordering multiple shoes you can ask to have my USA partner take the shoes out of the original boxes before shipping. This will mean that you can't return the shoes to the store in USA, but it will save on the shipping cost. If you have the shoes removed from their inner shoe boxes before shipping then you can normally have two pairs shipped via cheap economy shipping.