Validating willingness to pay for your product
(getting paid is the first form of validation).
Ash Maurya • Running Lean: Iterate from Plan A to a Plan That Works (Lean (O'Reilly))
The Best Approach: Ask Customers to Pay Right Now
Ask Teresa: How Can You Test a Customer’s Willingness to Pay? - Product Talk
One technique I like for gauging value is to see if the user would be willing to pay for it, even if you have no intention of charging them for it. We're looking for the user to pull out his or her credit card right then and there and ask to buy the product