leave it on auctions for 70-80% of the price. Or put it on the TP for the lowest price (10% or so and type like "willing to haggle" or "quicksale" etc.)
I have a couple MPs that I have yet to sell, I have sold quite a bit though. Just takes time, eventually you will find a buyer even if you leave it on the TP. For faster money try auctioning it a couple times at a discounted price of the TP like others said.