Just a thought - I saw a guy successfully repair an aluminum mast that broke in half just above the spreaders. He cleaned up the ends and welded an aluminum collar that wrapped around the mast - about a foot in height. Worked great.
The only problem is most welders cannot properly weld aluminum, so you need to find a specialist that does that kind of work.
So depending on the nature of the damage this may be an option - it has to work out a lot cheaper than a replacement mast.