Agawulf,
As a person who does many bcnm20's and a few 40's, we always agreed that the person who listed an item for sale retained the seller's fee. That is especially true now with the higher sales price. For example we recently recieved a Thunder Spirit pact which the last 5 sold at 200k. It cost my 3700g to list at 180k and ah relisted at 150k after it was returned to me. Ah listed it at 150,001 gil and it cost me 2700, so ah retained 6400g for sales fees and split the 193,600g three ways.
Personally this is fair to me and those ah do it with. Hopefully others see the fairness, and if they have trouble with it then they should back out of the bcnm before it's done.