Its a solid tank, the decors not the greatest but I would pay 50 or 75 and sell the fish stock off if you don't want them. Still cheaper than buying a new 55 for 100 bucks tank only.
I would pay up to $50. I got a free 55 gal and 30 with crappy set up's. Now they are really nice. Take what you can get and if it needs fixin, fixit. Maybe you could make it nice and resell it if you don't need it.
I haven't paid for a tank in a long time. Usually you can find anything 55 gal and smaller from someone that is getting out of fish because they don't know what they are doing. I've gotten 3 free 55 gals with stands this year alone. Of course I've dismantled them all because I hate the dimensions and I can use the glass for tinkering!
Take it if it's free. Who cares about cleaning it and etc. that's no biggie. A 55 is 50 bucks here. If it comes with filtration and a heater and their not cheapies I would pay a total of 75 tops. great tank though.