It seems crazy that someone actually asked me this but the reasoning behind the question is solid. Many people do not understand how brokers like us can offer to list a home on the MLS for a few hundred dollars when other real estate brokers charge a small fortune for their services.
Basically no one can set fees or I should say "create a standard fee" for real estate commissions because they would be violating the Sherman Anti Trust Act. This also means that brokers need to set their fees independently without any discussion what so ever with their competitors.
The great thing about this is that in the end the consumer wins. They win by being able to choose the type of service that they want to buy without being forced to pay for services that they do not want.