Once an end-user is set up on the product, he expects to seamlessly realize initial value that will make him come back for more. And this has to happen before the paywall.
Living in the “try before you buy era” users expect to taste products’ superpowers prior to any purchase. No matter how unique your solution is, paywalls need to follow rather than lead your “aha moment”. In the opposite case scenario, it will feel like a broken promise on the call-to-action that brought the end-user to you, and he will bounce.