If it's a warranty issue the retailer is required to pay postage according to the ACCC, but if it's not then the consumer pays unless the retailer has a special policy (like Amazon's free returns). I don't know anyone that would call a damaged box a warranty issue.
I know people in the Star Wars toy community get really upset over damaged packaging so it is a little odd to see a business that focuses on Star Wars toys take that approach. That said though they are right that most Transformers collectors don't care.
When I get my Grand Max from them while I would like the package to be in good shape I'm not going to worry ultimately if it has a couple of dings because even though I keep my Takara Tomy boxes it's just going to get flattened and kept with the rest of the large boxes behind a bookshelf.