I meet with customers regularly and I've come to the conclusion (so far) that value proposition is in the eyes of the beholder. The beholder of value is the prospective customer and the customer. Not the sales dude, the marketing guy, the owner, the president of your company. The biggest risk we all take is not staying in touch with the customer and diligently assessing their "value compass".
Value propositions, those statements that people use to "define" what's unique about their company, products and services can be dangerous. Why? I think too many companies establish a "value prop" and then hang their hats on it. It then sits in the corner gathering dust.
I'm of the view that customers are more interested in meaningful relationships with you and depending on what's important to them they define what value they want and need. This may sound a bit confusing but I'm learning that each customer picks tangible and intangible things from what you offer AND do with/for the customer....and they constantly reassess that value based on their ongoing experiences or lack of experiences with you.
These value priorities are contingent on what matters to the customer at that given moment in time both personally and professionally. You can't waive a generic value proposition in a someones face and expect them to go "ya, great that's exactly what I need". What you can do though, is give examples of how others are getting value from their relationship with you. This creates a meaningful conversation which can lead to a meaningful relationship.