Gee ... I don't have a pond or even live near you but free Koi sounds like a great deal for someone! I googled and found some Koi that are rather pricey $$$$$ for even one fish!
http://www.mokoi.com/koiforsal...
http://www.livekoiforsale.com/
I agree with NJBob, you could probably find a local fresh water aquarium shop who'd be willing to take them on trade! My husband has a 150 gallon marine (salt water) aquarium and when the coral's grow too large for the tank he trades them to local aquarium shops for other fish, coral or aquarium supplies.
Or, even if you can only get $5 apiece ... if you have a lot to sell you'd have extra spending money for something else ... like gardening supplies (if you're a gardener!)