My understanding is that the agent makes 10% of everything you get, because most agent contracts are exclusive. Agent puts me on Dune 2, agent gets 10% of my pay; I get on Dune 3 because they loved me so much in Dune 2, agent still gets 10% because our contract says she does, unless I fire her in time, which carries reputational risk.
I wonder, do people have agents on soap operas, which are probably the closest analogy to corporate software, i.e. projects that go on potentially forever and have some people spending their entire careers working on them?
(I had a neighbor who was a soap producer, but not in the US, so not a good source of info for this.)