Yeah that's the trouble with this case. Some folks would LOVE to have the pond others could care less...
I also think it makes a difference if it's well managed at the time of sale. If you can boast you can catch 9 inch BG and 3 plus pound bass out of your pond I think that would be a plus!!
Some folks may think that's just to big and don't want to mess with it. IMO I think the perfect pond would be about 2.5 to 3 acres but that's just me.
Would you get your money back out of it if you fixed it I am sure you would and maybe even more but you may have to wait for the right buyer is all...
Good Luck
RC