Maybe, if money issues are really a problem, why not give permissions to some users, so they start copying the threads and important information of some specific board, and then start migrating it here? That would reduce the overall time of the migration, and thus the total costs of it. Also, it would work in case of data loss or some big problem like that, because in that case you'll have mini- databases scattered around the Internet, and data would be saved.
Just my 2 cents. Feel free to critique