I was a licensed Realtor WAYYYYYYYY back in the early 90's...before all this Internet thang was happening.
I am not 100% certain on the answer to your question but keep in mind that being licensed to list and sell real estate is *not* the same as being a Realtor. "Realtor" is a brand name...it's an association...a "club," if you will. To "have the honor" of carrying the "Realtor" designation, you have to join the club...there's membership fees and dues.
I *believe* this is how the MLS is funded. Unless realtor.com has changed the way the National Association of Realtors does business, those dues completely fund the MLS. An agency's broker *may* have to pay a percentage of transactions to continue to fund the MLS but that's not an expense for the agent...or at least it didn't used to be.
I really don't remember if there were monthly dues for agents...I know there was a fee to join the NAR and annual dues. I just can't recall there being any ongoing NAR fees to agents besides the annual. And remember that having a real estate license does not give you the right to go out and list and sell real estate...you can only do it by "hanging your license" with a licensed Broker. Technically, all actions an agent takes are on behalf of his Broker, not him/herself. And, likewise, the Broker has additional expenses that the agent will not see or pay into unless they are in a 100% office like a Re/Max where agents pay for "desk space" and keep 100% of the commissions instead of splitting (usually 50/50) with their broker.
I think I said way too much considering I don't have the answer to your question, specifically
