That would be a more correct view.

In much debate and discussion I see "market value" substituted for "value". Often the implication is a vague one, as withmuch equivocation. pg's argumentventures there.

Keep in mind that Smith, Ricardo, and Marx each commit this error, including in the Smith passage I quoted. So do the Marginalists, or at leaast most of them.

Mariana Mazzucato may be an exception. (I've just discovered her, still going through her work.)

https://www.ted.com/talks/mariana_mazzucato_what_is_economic...

Separating value and price is 101 of marginal economics.

There couldn't be consumer surplus without it. I don't know how you could be marginalist and believe market price = value for user.

In theory. In practice just about every quantitative method or metric used to measure social welfare or individual well being falls back on price. And since our culture has a fetish for positivism and anything that looks like “math” those are the fixed assumptions that guide our decision making.

The fundamental principle of marginalism is, er, marginalism: that the derivative of supply or demand functions is what determines market price (not to be confused with "value", though it often is). The marginal cost or value.