But how do you measure "value"? "Value" has a large subjective and ephemeral aspect to it that can't readily be expressed in purely monetary terms.

You can't answer your question until you know who your target audience is, what problems they have that you're trying to solve, and how much those problems are costing them (in money, time, and annoyance). A thing may have no value at all to one person, but have enormous value to another. Finding your market is really just locating the audience who is bothered by the problem your product or service is solving.