what does this mean exactly?

[trojan10_om]

 Know the price of everything and the value of nothing

[Quizmonster]

This is a quote from Oscar Wilde's 'Lady Windermere's Fan'. It is, in effect, the definition of a cynic. That is, someone who chooses not to believe in goodness, selflessness etc. Such a person is always happy to put a monetary value on things, failing utterly to grasp that things can also have sentimental value that is actually priceless.

[ChocClare]

This phrase is Oscar Wilde's definition of a cynic: someone who knows the price of everything and the value of nothing.  A cynic, as I'm sure you know, is someone who always believes the worst of other people, and refuses to believe that anyone could act from any motive other than a selfish one.

[jenstar]

In the play, this definition of a cynic produces the response "And a sentimentalist, my dear Darlington, is a man
who sees an absurd value in everything, and doesn't know the market price of any single thing".

In fact, "Lady Windermere's Fan" is probably the most quotable of all Wilde's works. The very same scene also includes the much-quoted line " we are all in the gutter, but some of us are looking at the stars."

[Peter Pedant]

On another tack, this is what p*sses off Irene about Soames Forsyte in the Forsyte saga, although she doesnt quite say it.