I would imagine that all those engines drive up the weight and the size of the shipping box would be quite large too add in that because of the Chinese Virus prices have gone up. Your deal is a better than what my agent quoted me for DHL because USPS was no longer accepting packages from Japan EMS. All I had in my package was 1 bridge and 2 coaches which, without packaging weighed in at just under 16oz. They said it would be $145.00 dollars for just that???
There have been many of us here that have had huge packages of trains delivered from Japan at considerable prices, spending thousands on shipping. For that fast of shipping with DHL, in these times, I don't think thats a bad price for the load you are getting. Plus, in my experience with DHL they have super fast Customs for some reason even in these times, don't know why though. If saving money on shipping is what you want, surface shipping (by boat) is the cheapest but may take 3 months to get to you.