It’s actually over $0 and a lot of good will (something trolls might not understand).
The OP is not making any money on this. But it has a much higher potential loss than $100.
Every photographer should have an IP lawyer they know by name, because they (should) be used all the time. Every time you have to update your contracts, you should have him look over it and fix any missing legalese. And yeah, they are indeed inexpensive if it’s really basic stuff. If they have to research, then it goes up fast.