What is rehearsal packing?

I have ordered some items which weigh about 7kg. When i wanted to confirm the shipping the lowest price was about 170$ which is insane considering i have friends who got their items shipped for 80$(5-6 kg). I even removed the packaging for the shoes and i don't really want to spend that much on shipping. I've seen many comments about how rehearsal packaging reduced the total cost of the shipping significantly and i was wondering what does it mean. Pls help, thanks in advance!

https://preview.redd.it/zem5ury7rh0e1.png?width=2214&format=png&auto=webp&s=f6445502f2f094f1b6bb811433747655ef74963e