+1 there’s nothing preventing a seller from insisting on a graduated commission structure. In hot markets like SV agents love to be the selling agent. In fact given the low probability of a successful purchase with buyer competition, getting listings may even be the #1 skill/attribute of a successful agent.

Agents regularly engage in client management. The best agents can manage counterparty agents and get a deal done to close the buyer/seller gap. Clients have a lot of room to perform more stringent agent management in hot (ie liquid) markets.