Client: I can’t pay that much for this project.
Me: Okay, how about this- I give you a 40% discount and in return I get 10% royalties from any sales of the game, gross, in perpetuity.
Client: Make it a 50% discount and we’re good!
Me: Yeah, that sounds fine. Here’s the contract.
Client: …Once you’ve received full payment, all royalties would be cut, correct? There’s no mention in the contract of your royalties in perpetuity ending after you’ve made back your full original fee.
Somebody doesn’t know what “in perpetuity” means.