I’m no expert in shipping but will tell you what I know. Shipping brokers can be really helpful, but I think they are mainly looking for volume. Thus, someone who regularly ships, like a manufacturer, is going to get a much better rate than you are as a civilian.
When I was shipping stuff back and forth to Slovenia, pre-Covid, Franc Kuzma could send something overnight, using his account, for less than it cost me to ship a cable across the country that was insured for low fair value (not necessarily retail replacement).
Shipping has gotten way more expensive in the last couple years. The bigger the vendor, the better their leverage if they pass it onto you.
For big stuff, I palletize, use wooden crates and air freight.
I knew a guy who shipped priceless cars all over the world by air- back in the day, it was 5 grand to load and fly one from NY to the Mid-East. Now, it’s probably at least triple that price.
If you are working with or shipping to someone who has a business account, they may be able get a better price than you.