The customer interview question that actually works
Forget "would you pay for this." Forget "what would you change." There's one question that consistently surfaces the real story.
Most customer interview questions invite the customer to be polite, hypothetical, or strategic. Politeness is useless data. Hypotheticals are unreliable. Strategy is what you're paid to do, not them.
The question
"Walk me through the last time you tried to do this. What were you using? What broke? What did you do about it?" Past tense. Specific. About them, not your product.
Why it works
People can describe what they did with precision. They struggle to predict what they would do. They lie about what they'd pay. They tell the truth about what they hacked together yesterday. Build for the people who already hacked something together — those are the ones whose problem is real.
Don't ask what they'd want. Ask what they last tried.