I couldn't find anything in the wiki explaining what should be an obvious question

If I want to transfer files between my accounts I guess I need to buy the Export and Import add-ons.

To move files from Dropbox to Box.net do I need to Export from one acct and Import to the other? 

If I want to also copy files from say Amazon Cloud Drive to Box.net do I need to buy another copy of the Import/Export add-ons, or is one copy good for all accounts?