This is very similar to what I did when I bought my boat. It was a 21' with a trailer from Tampa.
What brand of boat? I bought a used Mastercraft from the a dealer in Tampa. If you're buying it from a dealer as them who ships there boats from the factory.
In my case the dealer was getting their spring boats delivered direct from Mastercraft and the drivers usually go back empty or with one boat for warranty work and have room for others.
I had them take my boat back to the Mastercraft factory on their return from Tampa, it sat there about a week in the secured lot with the new boats. Then it shipped with the new boats going the local Mastercraft dealer in Fenton. In all I think it cost me less than $300 to ship it from Tampa to Metro Detroit.
If you're buying a from a dealer I would ask them who they use.