I sold TALL frame Marathon back in May on CL here, the bike was pretty clean when I got it so it didn't take much to make it a good rider.
I gave it new bar tape, two new cables, cleaned and repacked both hubs and the bottom bracket and listed it for $300 obo. It was gone in four days for $225 to a guy who wanted to make a fixie out of it.
I don't think its selling price had much to do with the make or model, just its frame size. BIG bikes sell fast here for some reason.
I had a smaller frame version of it here at the same time in near mint condition, and it never sold. I went all the way down to $50 and got no takers I finally parted it out and got $75 for the wheels, and more than $150 out of the rest of the bike in pieces. It all sold except for the frame and fork.
To be fair, the norm around these parts is that bikes don't sell unless you give them away for $10 to $20 tops, and the department store stuff sells best.
I guess its a brand recognition thing.