How good was this deal, exactly?
Unless they were paying you to take the ESC off your hands, I can't see how you could get much cheaper than the ~20A brushless ESCs already on the market.
Keep the brushed one, though. You can use it to run lights or other things on your planes that need controllable direct current. I've used an 18A brushed ESC to run a bunch of LEDs on a foam flying wing. Turned them on and off with the flap switch. Awesome