I list the majority of my domain names for sale on GoDaddy via its Afternic distribution network. These are the easy to replace inventory types of domain names I try to buy and/or sell every day for reasonable prices and returns. Some of my most valuable domain names are not listed for sale via GoDaddy though.
When one of my domain names that is listed for sale on Afternic gets an offer, a broker typically contacts me to let me know how much the prospective buyer is willing to pay. GoDaddy is working on my behalf on this type of negotiation, and they work with the buyer to try and get a deal done at my asking price or close. If a deal is successful, I am responsible to pay the full commission. By way of example, if someone offers $2,000 for my domain name and I take it, I will net about $1,600.