Sad truth is if you didn't buy it, it would probably still be sitting there in their shed.
You cousin is only mad at him or herself for their own lack of knowledge on it's value before the sale.
PS. It's never a good idea to do business with a relative.
My one Uncle had a lot of horse drawn machinery, he gave me four beautiful pieces which I repainted. He is gone now, bless his soul, and there is still a lot of equipment there some new pieces too but I won't even ask for any of it.