I would like to buy a recipe for hot fudge topping from someone I know. It was given to him by a church friend handed down for years before he got it. He then made 40 batches or so he said, to come up with a great hot fudge which I would like to serve at my ice cream store. He use to sell the hot fudge to me but stopped as he moved on to other things. I'd like to buy his recipe instead of attempting to "reinvent the wheel." I did a taste test with some of my staff against the commercial junk we are using now and it was unanimous his was much better. I don't mind paying for it as I plan to make money off it but me thinks he wants too much. I want to be fair but I don't want to be taken advantage of. How to I calculate what his recipe is worth?