The worth of a turning can have two meanings; price and value.
I'm not so sure. An item of extremely high worth may actually be priceless.

Price can
be determined by formula. It's variables a time, equipment, shop,
materials, learning, experience and all the costs of selling.
You forgot to add the turner's reputation. That can multiply the price, all
other things being equal.

Value is determined by what the buyer gets out and will pay for, not by
what the turner puts in. A turning's quality has nothing to do with how
expensive or novel it is or how hard it is to make.
The easy test for value is to keep changing your price and see what happens to
sales. You will soon find the optimal balance between price and quantity sold.

Nothing is more tiresome than someone who believes he has had
an original thought and feels compelled to bray about it. Anyway, I'd
enjoy reading yours, whether you agree or not. Arch
Not to me. Original thoughts are hard to come by. Many people go through their
entire lives without having one. If someone has an original thought I think they
have a right to brag about it.