For a CW filter one can get as much as $200, about half what one can get for a used FT817.? But having the filter in the rig will make it sell quicker and for more.
I have the Collins 500 Hz filter in my FT817.? I do need to sell it for dont use, I have the IC705 and X6100.? But I have always liked my FT817, very good QRP rig.