What is the typical payment arrangement for course design?
Did you agree to design the courses before talking about payment?  I don't know if you have any recourse at this point as there was never a contract in place.  I would guess that had you inquired ahead of time, your superiors would probably have asked someone else to do it for free, as that is probably what they were expecting.

If there is a system in place for paying you for the course design, I would assume it would be a one-time payment with no residual payments, and you should work that out before beginning design.  If you can work something out where you do get royalties down the road, that also needs to be in a contract, and I would be very surprised if you were able to pull it off (but good luck!).