What would you pay?

[rocketlily]

I have been sold for $0.00 a used Aqua-Tech 20-40 Filter. This originally came as part of a complete package with a new tank. It was used for a few years in a Chiclid tank, and has been replaced with a Whisper filter. It was "sold" to me, as I broke my Nano Skimmer while cleaning it (always did hate it and not sorry I broke it). I will be using it on my 10 gal nano tank for the nano contest.

Now I must determine the fair market value. What would you pay for this filter, used and not including any filter cartridges?