There is no royalty for custom work-for-hire fees, so if your Product (under the EULA) is a custom simulator for single client, then your contractor fees are royalty free.
As for your client’s use, it sounds like they are selling access to the simulator (in addition to associated training services) - is that right?
Note that unless your client also becomes a EULA licensee, you (rather than them) are responsible for royalties (if there are any).