Re doing it yourself using
project shipping (ie your "like a back load or some other little known method" request) - I suspect this will not turn out to be attractive unless you are very lucky. I also suspect that the cost of any form of transport is likely to be unattractive unless the boat is of high value.
I have had a couple of around 80 foot new
power boats transported as deck cargo as a
project over a longer
passage than you plan by Clipper Elite Carriers ships -
www.cecshipping.com with no problems. You will see that they have project offices in both
USA and Australia but I don't know how interested they would be in a small load though. The passage was on a ship that was essentially empty after unloading but its
route to its next port of loading fitted us with little deviation.
Cost may depend on the availability of the ships and their routing matching your needs, but if you are flexible timing wise that may become easier. You will have to get the boat to the ship, meet a strict loading window and may pay a large penalty if you miss it or otherwise cause the vessel a delay. Cost of the supporting
cradle for the boat on deck may be considerable, be required to be approved by the ship if they are not providing it and the
insurance risk for shipped
keel boats is relatively high compared to many other cargoes. You will also have to make sure all entry and exit costs,
taxes, duties, other
documentation, stevedoring, land transport, etc are being taken care of by someone and you yourself or someone authorised by you may be required by the project ship's master to be on hand at loading and unloading to sign the cargo off as received in good condition (in my case I was authorised by the owner of the boats to do this and we also arranged to have a representative of the insurer on board to inspect the loading to avoid arguments with them later if damage occurred then or during the passage).
You could use a logistics company to do all this for you but I suspect that will take you back to the result you have now - regular shipping.
I would be surprised if you made significant gains on the price you mention though compared to shipping by regular services, especially if the boat will fit into a 40 foot container the internal height of which is a little under 2.4 meters so almost sure to be too little
headroom, or 2.7 meters for a 40 foot High Cube one which might just squeeze in if your boat is of
shallow draft (boat weight is not a problem) - but I have never shipped a boat in a container to be sure of the cost advantage. If the
mast won't fit in the 40 foot High Cube container see if a 45 foot High Cube is available, otherwise, a long shot but I would look at sending the
mast by air. The logistics company you should talk to if intending container or other regular shipping may have other suggestions for all this - I would also ask about letting them use spare space in the container for their other client cargo should you be able to fit the boat in a container, especially if a 45 foot container.
The case I mention was part of a bigger project so I can't remember the final shipping costs but was originally estimated to be approx USD100,000 per boat but turned out to be considerably more, that a few years back. It was a slightly longer passage than you contemplate and did not require cradles (they were cats so were able to be sat simply on timbers laid on deck - the shipping need was known when they were designed so they also had tie down points already built into their structure, so all very simple) - in this case loading/unloading was to/from the sea so no stevedoring charges applied either.