The fee can be negotiable but don't forget if you negotiate much lower than 6% many buyer's agents will not want to show your property due to the lower commission. You can win one side but lose on another.
If you want to discuss further please contact me as I specialize and live in Miami Beach.
The Campins Co.
There are two sides to the commission equation, the amount you offer to the listing agent and the amount you offer to the buyer's agent that actually gets your property sold.
With a 5 million property you should have a lot of room on discounting the "listing" side. In fact an agent may even agree to list it for "free" just to get those $5 million dollar leads!
All the best,