what is a fair price, for both seller and buyer, for a used but functional AMP BH-420? I ask, because though they are much older and "can be had for great prices in the used market" so i hear so frequently on Message boards online, i NEVER see the used around where i live. also, if they are so good, doesnt that mean they will start to command higher prices ? anyway, i am wondering what those of you who are EDUCATED consumers and sellers would consider a FAIR price whether you were selling or buying. thanks.