Up to a point. They get a fraction of the marginal increase in salary, and they’d much sooner “close the sale” than risking having someone else fill the job to try and get an extra 500$ commission.
It’s the same story with real estate agents: selling your house for an extra 20k might be a lot to you but to the agent it’s an extra 400$ in commission (exact percentage varies). In other words, it’s hardly worth risking the seller losing interest or working an extra 2–3 weeks for so little.