This question and topic is totally worthy of a doctoral dissertation or a lengthy cross-country motorcycle road trip with friends while confronting the ghost of Phaedrus :-) But for today’s mundane practical matters of designing a product that is valuable to a target audience, I’d humbly suggest value just comes down to a few basic, essential questions.
In my view, value is an immaterial, emergent quality that arises from a person’s interaction with something (physical / virtual / social) which clearly answers:
a) what task does this “something” help me accomplish
b) what goal does this “something” help me fulfill and
c) how does this “something” make me feel–the emotional benefit.
And…becomes something that enables a positive habit of use, weaving itself into fabric of living, working, playing, etc. to the point it’s necessary to a good life…while, of course, supporting the business too, not just in a financial value sense, but in a “gives the business a purposeful driver for its existence” sense, shaping its way into the life of ordinary folks.
Value in this humanist sense is about personal relevance, and meaning— at functional, social, cultural, even spiritual (or self-reflective) levels. The significance of a design is found not in the gazing upon the visual mockup, but in the daily engagement of the profound, incorporated in the pixels and atoms through the designer’s empathetic and aesthetic vision.
Value is found in convenience, comfort, assurance, empowerment, confidence, trust, safety, joy, and other personal aspirations that enable a “good life”.
What “value” your product aspires to deliver is the most difficult question to answer as that will drive the feature priority, the experience journey, the resulting outcomes. Indeed, what it is you are making! Just keep returning to the 3 key questions above re: task completion, goal fulfillment, and emotional benefit. And what is that central umbrella concept (like comfort or joy) that this product or feature promises to deliver? That’s the value proposition. Not some jargon-filled, committee-based awkward company statement that makes eyeballs roll. Value is what makes people love your product and believe in its ability to make their lives better.