In case your confused, you can lock all the tune files you want.........you can put the restrictions on the tuning file and all someone has to do is read out the "CANNOT BE READ OR MODIFIED" tune you just permission restricted and they have the copy of the tune.

So locking the controller is the only way to secure the file.

Autolocking controllers for E54 and E60 solves the issue you are experiencing, why anyone would want $300 to unlock it is beyond me, unless they are not selling many ecms and want to make some $$$$$ by unlocking them.