When is an insight not strong enough for a value proposition?

One of the most frequently asked questions on my training courses is "When will I know whether my customer insight is strong enough to form the basis of a compelling value proposition?". In essence, how would a team know whether to invest time and resources building a product based around a particular problem? It's the $64,000 dollar question, or perhaps for some of you, given the investment and R&D dollars [...]